AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/08/04 07:16	flow	patch-triage	7m Args: null Results: { "EnableConfigs": [ "BLK_CGROUP", "BLK_CGROUP_IOLATENCY", "BLK_CGROUP_IOCOST", "BLK_CGROUP_IOPRIO", "IOSCHED_BFQ", "BFQ_GROUP_IOSCHED", "NVME_FC", "BLK_CGROUP_FC_APPID", "BTRFS_FS", "MEMCG", "BLK_DEV_THROTTLING", "BLK_DEV_MD", "BCACHE", "BLK_DEV_DM", "BLK_INLINE_ENCRYPTION", "BLK_INLINE_ENCRYPTION_FALLBACK", "GFS2_FS", "BLK_DEV_PMEM", "VIRTIO_PMEM" ], "FocusSymbols": [ "bio_blkg_lookup", "bio_blkg", "bio_associate_blkcg_from_css", "bio_associate_blkcg", "bio_clone_blkcg_association", "bio_put_blkg_ref", "blkcg_punt_bio_submit", "bfq_bio_bfqg", "blkcg_get_fc_appid", "blkcg_set_ioprio", "__blk_throtl_bio", "bfqg_stats_update_legacy_io", "blk_cgroup_bio_start" ], "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.", "WorthFuzzing": true }
1/1	2026/08/04 07:16	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 37ab22cb5f20111358288fbe1554a0d2e13b1a8a\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Tue Aug 4 07:16:16 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst\nindex 14b8c571c0d14..bbd79931d5ab5 100644\n--- a/Documentation/admin-guide/cgroup-v2.rst\n+++ b/Documentation/admin-guide/cgroup-v2.rst\n@@ -3235,7 +3235,7 @@ the configuration, the bio may be executed at a lower priority and if\n the writeback session is holding shared resources, e.g. a journal\n entry, may lead to priority inversion. There is no one easy solution\n for the problem. Filesystems can try to work around specific problem\n-cases by skipping wbc_init_bio() and using bio_associate_blkg()\n+cases by skipping wbc_init_bio() and using bio_associate_blkcg()\n directly.\n \n \ndiff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c\nindex e82ff03bda02e..3ac3b4c054026 100644\n--- a/block/bfq-cgroup.c\n+++ b/block/bfq-cgroup.c\n@@ -363,11 +363,13 @@ void bfqg_and_blkg_put(struct bfq_group bfqg)\n \n void bfqg_stats_update_legacy_io(struct request_queue q, struct request rq)\n {\n-\tstruct bfq_group bfqg = blkg_to_bfqg(rq-\u003ebio-\u003ebi_blkg);\n+\tstruct blkcg_gq blkg = bio_blkg_lookup(rq-\u003ebio);\n+\tstruct bfq_group bfqg;\n \n-\tif (!bfqg)\n+\tif (!blkg)\n \t\treturn;\n \n+\tbfqg = blkg_to_bfqg(blkg);\n \tblkg_rwstat_add(\u0026bfqg-\u003estats.bytes, rq-\u003ecmd_flags, blk_rq_bytes(rq));\n \tblkg_rwstat_add(\u0026bfqg-\u003estats.ios, rq-\u003ecmd_flags, 1);\n }\n@@ -606,7 +608,7 @@ static void bfq_link_bfqg(struct bfq_data bfqd, struct bfq_group bfqg)\n \n struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio)\n {\n-\tstruct blkcg_gq blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq blkg = bio_blkg_lookup(bio);\n \tstruct bfq_group bfqg;\n \n \twhile (blkg) {\n@@ -614,14 +616,16 @@ struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio)\n \t\t\tblkg = blkg-\u003eparent;\n \t\t\tcontinue;\n \t\t}\n+\n \t\tbfqg = blkg_to_bfqg(blkg);\n \t\tif (bfqg-\u003epd.online) {\n-\t\t\tbio_associate_blkg_from_css(bio, \u0026blkg-\u003eblkcg-\u003ecss);\n+\t\t\tbio_associate_blkcg_from_css(bio, \u0026blkg-\u003eblkcg-\u003ecss);\n \t\t\treturn bfqg;\n \t\t}\n \t\tblkg = blkg-\u003eparent;\n \t}\n-\tbio_associate_blkg_from_css(bio,\n+\n+\tbio_associate_blkcg_from_css(bio,\n \t\t\t\t\u0026bfqg_to_blkg(bfqd-\u003eroot_group)-\u003eblkcg-\u003ecss);\n \treturn bfqd-\u003eroot_group;\n }\ndiff --git a/block/bfq-iosched.c b/block/bfq-iosched.c\nindex 0f75301b3115f..3d51d743552cb 100644\n--- a/block/bfq-iosched.c\n+++ b/block/bfq-iosched.c\n@@ -128,6 +128,7 @@\n \n #include \"elevator.h\"\n #include \"blk.h\"\n+#include \"blk-cgroup.h\"\n #include \"blk-mq.h\"\n #include \"blk-mq-sched.h\"\n #include \"bfq-iosched.h\"\n@@ -2452,15 +2453,15 @@ static bool bfq_bio_merge(struct request_queue q, struct bio bio,\n \tstruct request free = NULL;\n \tbool ret;\n \n+#ifdef CONFIG_BFQ_GROUP_IOSCHED\n+\tif (bic \u0026\u0026 bio_blkg_lookup(bio) == NULL)\n+\t\treturn false;\n+#endif\n+\n \tspin_lock_irq(\u0026bfqd-\u003elock);\n \n \tif (bic) {\n-\t\t/\n-\t\t Make sure cgroup info is uptodate for current process before\n-\t\t * considering the merge.\n-\t\t /\n \t\tbfq_bic_update_cgroup(bic, bio);\n-\n \t\tbfqd-\u003ebio_bfqq = bic_to_bfqq(bic, op_is_sync(bio-\u003ebi_opf),\n \t\t\t\t\t bfq_actuator_index(bfqd, bio));\n \t} else {\n@@ -6245,6 +6246,13 @@ static void bfq_insert_request(struct blk_mq_hw_ctx hctx, struct request rq,\n \tLIST_HEAD(free);\n \n #ifdef CONFIG_BFQ_GROUP_IOSCHED\n+\t/\n+\t * Pin the blkg used to look up bfqg. If this is the first IO for\n+\t * the blkcg on this queue, create the bfqg before holding bfqd-\u003elock.\n+\t /\n+\tif (rq-\u003ebio \u0026\u0026 !bio_flagged(rq-\u003ebio, BIO_BLKG_REF))\n+\t\tbio_blkg(rq-\u003ebio);\n+\n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 rq-\u003ebio)\n \t\tbfqg_stats_update_legacy_io(q, rq);\n #endif\ndiff --git a/block/bio.c b/block/bio.c\nindex 6a2f6fc3413e8..db33c993c2964 100644\n--- a/block/bio.c\n+++ b/block/bio.c\n@@ -179,12 +179,7 @@ static inline gfp_t try_alloc_gfp(gfp_t gfp)\n \n void bio_uninit(struct bio bio)\n {\n-#ifdef CONFIG_BLK_CGROUP\n-\tif (bio-\u003ebi_blkg) {\n-\t\tblkg_put(bio-\u003ebi_blkg);\n-\t\tbio-\u003ebi_blkg = NULL;\n-\t}\n-#endif\n+\tbio_clear_blkcg(bio);\n \tif (bio_integrity(bio))\n \t\tbio_integrity_free(bio);\n \n@@ -233,10 +228,10 @@ void bio_init(struct bio bio, struct block_device bdev, struct bio_vec table,\n \tbio-\u003ebi_end_io = NULL;\n \tbio-\u003ebi_private = NULL;\n #ifdef CONFIG_BLK_CGROUP\n-\tbio-\u003ebi_blkg = NULL;\n+\tbio-\u003ebi_blkcg = NULL;\n \tbio-\u003eissue_time_ns = 0;\n \tif (bdev)\n-\t\tbio_associate_blkg(bio);\n+\t\tbio_associate_blkcg(bio);\n #ifdef CONFIG_BLK_CGROUP_IOCOST\n \tbio-\u003ebi_iocost_cost = 0;\n #endif\n@@ -281,7 +276,7 @@ void bio_reset(struct bio bio, struct block_device bdev, blk_opf_t opf)\n \tbio-\u003ebi_io_vec = bv;\n \tbio-\u003ebi_bdev = bdev;\n \tif (bio-\u003ebi_bdev)\n-\t\tbio_associate_blkg(bio);\n+\t\tbio_associate_blkcg(bio);\n \tbio-\u003ebi_opf = opf;\n }\n EXPORT_SYMBOL(bio_reset);\n@@ -865,7 +860,7 @@ static int __bio_clone(struct bio bio, struct bio bio_src, gfp_t gfp)\n \t\tif (bio-\u003ebi_bdev == bio_src-\u003ebi_bdev \u0026\u0026\n \t\t bio_flagged(bio_src, BIO_REMAPPED))\n \t\t\tbio_set_flag(bio, BIO_REMAPPED);\n-\t\tbio_clone_blkg_association(bio, bio_src);\n+\t\tbio_clone_blkcg_association(bio, bio_src);\n \t}\n \n \tif (bio_crypt_clone(bio, bio_src, gfp) \u003c 0)\n@@ -1803,17 +1798,12 @@ void bio_endio(struct bio bio)\n \t\tgoto again;\n \t}\n \n-#ifdef CONFIG_BLK_CGROUP\n \t/\n \t Release cgroup info. We shouldn't have to do this here, but quite\n \t * a few callers of bio_init fail to call bio_uninit, so we cover up\n \t * for that here at least for now.\n \t /\n-\tif (bio-\u003ebi_blkg) {\n-\t\tblkg_put(bio-\u003ebi_blkg);\n-\t\tbio-\u003ebi_blkg = NULL;\n-\t}\n-#endif\n+\tbio_clear_blkcg(bio);\n \n \tif (bio-\u003ebi_end_io)\n \t\tbio-\u003ebi_end_io(bio);\ndiff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c\nindex 3ec21333f393b..7589c62099898 100644\n--- a/block/blk-cgroup-fc-appid.c\n+++ b/block/blk-cgroup-fc-appid.c\n@@ -50,8 +50,14 @@ EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);\n /\n char blkcg_get_fc_appid(struct bio bio)\n {\n-\tif (!bio-\u003ebi_blkg \|\| bio-\u003ebi_blkg-\u003eblkcg-\u003efc_app_id[0] == '\\0')\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n+\n+\tif (!blkcg)\n+\t\treturn NULL;\n+\n+\tif (blkcg-\u003efc_app_id[0] == '\\0')\n \t\treturn NULL;\n-\treturn bio-\u003ebi_blkg-\u003eblkcg-\u003efc_app_id;\n+\n+\treturn blkcg-\u003efc_app_id;\n }\n EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);\ndiff --git a/block/blk-cgroup.c b/block/blk-cgroup.c\nindex d9676126c5b5d..a70f92f1541b1 100644\n--- a/block/blk-cgroup.c\n+++ b/block/blk-cgroup.c\n@@ -170,10 +170,6 @@ static void __blkg_release(struct rcu_head rcu)\n {\n \tstruct blkcg_gq blkg = container_of(rcu, struct blkcg_gq, rcu_head);\n \n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tWARN_ON(!bio_list_empty(\u0026blkg-\u003easync_bios));\n-#endif\n-\n \tblkg_free(blkg);\n }\n \n@@ -206,19 +202,18 @@ static void blkg_release(struct percpu_ref ref)\n #ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n static struct workqueue_struct blkcg_punt_bio_wq;\n \n-static void blkg_async_bio_workfn(struct work_struct work)\n+static void blkcg_async_bio_workfn(struct work_struct work)\n {\n-\tstruct blkcg_gq blkg = container_of(work, struct blkcg_gq,\n-\t\t\t\t\t async_bio_work);\n+\tstruct blkcg blkcg = container_of(work, struct blkcg, async_bio_work);\n \tstruct bio_list bios = BIO_EMPTY_LIST;\n \tstruct bio bio;\n \tstruct blk_plug plug;\n \tbool need_plug = false;\n \n-\t/* as long as there are pending bios, @blkg can't go away /\n-\tspin_lock(\u0026blkg-\u003easync_bio_lock);\n-\tbio_list_merge_init(\u0026bios, \u0026blkg-\u003easync_bios);\n-\tspin_unlock(\u0026blkg-\u003easync_bio_lock);\n+\t/ as long as there are pending bios, @blkcg can't go away /\n+\tspin_lock(\u0026blkcg-\u003easync_bio_lock);\n+\tbio_list_merge_init(\u0026bios, \u0026blkcg-\u003easync_bios);\n+\tspin_unlock(\u0026blkcg-\u003easync_bio_lock);\n \n \t/ start plug only when bio_list contains at least 2 bios /\n \tif (bios.head \u0026\u0026 bios.head-\u003ebi_next) {\n@@ -239,15 +234,15 @@ static void blkg_async_bio_workfn(struct work_struct work)\n /\n void blkcg_punt_bio_submit(struct bio bio)\n {\n-\tstruct blkcg_gq blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n \n-\tif (blkg-\u003eparent) {\n-\t\tspin_lock(\u0026blkg-\u003easync_bio_lock);\n-\t\tbio_list_add(\u0026blkg-\u003easync_bios, bio);\n-\t\tspin_unlock(\u0026blkg-\u003easync_bio_lock);\n-\t\tqueue_work(blkcg_punt_bio_wq, \u0026blkg-\u003easync_bio_work);\n+\tif (blkcg \u0026\u0026 cgroup_parent(blkcg-\u003ecss.cgroup)) {\n+\t\tspin_lock(\u0026blkcg-\u003easync_bio_lock);\n+\t\tbio_list_add(\u0026blkcg-\u003easync_bios, bio);\n+\t\tspin_unlock(\u0026blkcg-\u003easync_bio_lock);\n+\t\tqueue_work(blkcg_punt_bio_wq, \u0026blkcg-\u003easync_bio_work);\n \t} else {\n-\t\t/* never bounce for the root cgroup /\n+\t\t/ Never bounce if there is no non-root blkcg to queue on. /\n \t\tsubmit_bio(bio);\n \t}\n }\n@@ -275,9 +270,9 @@ subsys_initcall(blkcg_punt_bio_init);\n /\n struct cgroup_subsys_state bio_blkcg_css(struct bio bio)\n {\n-\tif (!bio \|\| !bio-\u003ebi_blkg)\n+\tif (!bio \|\| !bio_blkcg(bio))\n \t\treturn NULL;\n-\treturn \u0026bio-\u003ebi_blkg-\u003eblkcg-\u003ecss;\n+\treturn \u0026bio_blkcg(bio)-\u003ecss;\n }\n EXPORT_SYMBOL_GPL(bio_blkcg_css);\n \n@@ -325,11 +320,6 @@ static struct blkcg_gq blkg_alloc(struct blkcg blkcg, struct gendisk disk,\n \tINIT_LIST_HEAD(\u0026blkg-\u003eq_node);\n \tblkg-\u003eblkcg = blkcg;\n \tblkg-\u003eiostat.blkg = blkg;\n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tspin_lock_init(\u0026blkg-\u003easync_bio_lock);\n-\tbio_list_init(\u0026blkg-\u003easync_bios);\n-\tINIT_WORK(\u0026blkg-\u003easync_bio_work, blkg_async_bio_workfn);\n-#endif\n \n \tu64_stats_init(\u0026blkg-\u003eiostat.sync);\n \tfor_each_possible_cpu(cpu) {\n@@ -1357,6 +1347,9 @@ static void blkcg_css_free(struct cgroup_subsys_state css)\n \n \tmutex_unlock(\u0026blkcg_pol_mutex);\n \n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tWARN_ON(!bio_list_empty(\u0026blkcg-\u003easync_bios));\n+#endif\n \tfree_percpu(blkcg-\u003elhead);\n \tkfree(blkcg);\n }\n@@ -1406,6 +1399,11 @@ blkcg_css_alloc(struct cgroup_subsys_state parent_css)\n \trefcount_set(\u0026blkcg-\u003eonline_pin, 1);\n \tINIT_RADIX_TREE(\u0026blkcg-\u003eblkg_tree, GFP_NOWAIT);\n \tINIT_HLIST_HEAD(\u0026blkcg-\u003eblkg_list);\n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tspin_lock_init(\u0026blkcg-\u003easync_bio_lock);\n+\tbio_list_init(\u0026blkcg-\u003easync_bios);\n+\tINIT_WORK(\u0026blkcg-\u003easync_bio_work, blkcg_async_bio_workfn);\n+#endif\n #ifdef CONFIG_CGROUP_WRITEBACK\n \tINIT_LIST_HEAD(\u0026blkcg-\u003ecgwb_list);\n #endif\n@@ -2046,129 +2044,181 @@ void blkcg_add_delay(struct blkcg_gq blkg, u64 now, u64 delta)\n \tatomic64_add(delta, \u0026blkg-\u003edelay_nsec);\n }\n \n-static inline struct blkcg_gq blkg_lookup_tryget(struct blkcg_gq blkg)\n+/\n+ Return the blkg pinned by @bio through BIO_BLKG_REF. The returned blkg is\n+ * already owned by @bio and no extra reference is acquired. If the pinned\n+ * blkg can't be found, fall back to the root blkg.\n+ /\n+static struct blkcg_gq bio_pinned_blkg(struct bio bio)\n {\n-retry:\n-\tif (blkg_tryget(blkg))\n-\t\treturn blkg;\n+\tstruct request_queue q = bdev_get_queue(bio-\u003ebi_bdev);\n+\tstruct blkcg_gq blkg;\n \n-\tblkg = blkg-\u003eparent;\n-\tif (blkg)\n-\t\tgoto retry;\n+\trcu_read_lock();\n+\tblkg = blkg_lookup(bio_blkcg(bio), q);\n+\trcu_read_unlock();\n \n-\treturn NULL;\n+\tif (WARN_ON_ONCE(!blkg))\n+\t\treturn q-\u003eroot_blkg;\n+\treturn blkg;\n }\n+\n /\n- blkg_tryget_closest - try and get a blkg ref on the closet blkg\n+ * bio_blkg_lookup - look up a blkg associated with a bio\n * @bio: target bio\n- * @css: target css\n \n- As the failure mode here is to walk up the blkg tree, this ensure that the\n- * blkg-\u003eparent pointers are always valid. This returns the blkg that it ended\n- * up taking a reference on or %NULL if no reference was taken.\n+ * Look up the queue-local blkg for @bio's current device and blkcg without\n+ * creating a missing blkg. The first successful lookup pins the blkg to @bio;\n+ * later lookups reuse the bio-owned reference.\n /\n-static inline struct blkcg_gq blkg_tryget_closest(struct bio bio,\n-\t\tstruct cgroup_subsys_state css)\n+struct blkcg_gq bio_blkg_lookup(struct bio bio)\n {\n-\tstruct request_queue q = bio-\u003ebi_bdev-\u003ebd_queue;\n-\tstruct blkcg blkcg = css_to_blkcg(css);\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n+\tstruct request_queue q;\n \tstruct blkcg_gq blkg;\n \n+\tif (bio_flagged(bio, BIO_BLKG_REF))\n+\t\treturn bio_pinned_blkg(bio);\n+\n+\tif (!blkcg \|\| !bio-\u003ebi_bdev)\n+\t\treturn NULL;\n+\n+\tq = bdev_get_queue(bio-\u003ebi_bdev);\n \trcu_read_lock();\n \tblkg = blkg_lookup(blkcg, q);\n-\tif (likely(blkg))\n-\t\tblkg = blkg_lookup_tryget(blkg);\n+\tif (blkg \u0026\u0026 blkg_tryget(blkg))\n+\t\tbio_set_flag(bio, BIO_BLKG_REF);\n+\telse\n+\t\tblkg = NULL;\n \trcu_read_unlock();\n \n-\tif (blkg)\n-\t\treturn blkg;\n+\treturn blkg;\n+}\n+EXPORT_SYMBOL_GPL(bio_blkg_lookup);\n+\n+/\n+ bio_put_blkg_ref - drop the blkg reference pinned by a bio\n+ * @bio: target bio\n+ \n+ Drop the bio-owned blkg reference acquired by bio_blkg(), if any.\n+ /\n+void bio_put_blkg_ref(struct bio bio)\n+{\n+\tif (bio_flagged(bio, BIO_BLKG_REF)) {\n+\t\tstruct blkcg_gq blkg = bio_pinned_blkg(bio);\n+\n+\t\tblkg_put(blkg);\n+\t\tbio_clear_flag(bio, BIO_BLKG_REF);\n+\t}\n+}\n+EXPORT_SYMBOL_GPL(bio_put_blkg_ref);\n+\n+/\n+ bio_blkg - look up the blkg associated with a bio\n+ * @bio: target bio\n+ \n+ Look up the queue-local blkg for @bio's current device and blkcg. If this\n+ * is the first policy use of @bio, create the missing blkg hierarchy if\n+ * necessary, pin the exact blkg, and mark @bio so bio_clear_blkcg() can drop\n+ * the reference when the bio completes.\n+ /\n+struct blkcg_gq bio_blkg(struct bio bio)\n+{\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n+\tstruct gendisk disk;\n+\tstruct request_queue q;\n+\tstruct blkcg_gq blkg;\n+\n+\tif (!blkcg \|\| !bio-\u003ebi_bdev)\n+\t\treturn NULL;\n+\n+\tif (bio_flagged(bio, BIO_BLKG_REF))\n+\t\treturn bio_pinned_blkg(bio);\n+\n+\tdisk = bio-\u003ebi_bdev-\u003ebd_disk;\n+\tq = disk-\u003equeue;\n \n-\t/\n-\t * Fast path failed, we're probably issuing IO in this cgroup the first\n-\t * time, hold lock to create new blkg.\n-\t /\n \tspin_lock_irq(\u0026q-\u003equeue_lock);\n-\tblkg = blkg_lookup_create(blkcg, bio-\u003ebi_bdev-\u003ebd_disk);\n-\tif (blkg)\n-\t\tblkg = blkg_lookup_tryget(blkg);\n+\tblkg = blkg_lookup_create(blkcg, disk);\n+\tif (blkg \u0026\u0026 blkg-\u003eblkcg == blkcg \u0026\u0026 blkg_tryget(blkg))\n+\t\tbio_set_flag(bio, BIO_BLKG_REF);\n+\telse\n+\t\tblkg = NULL;\n \tspin_unlock_irq(\u0026q-\u003equeue_lock);\n \n \treturn blkg;\n }\n+EXPORT_SYMBOL_GPL(bio_blkg);\n \n /\n- bio_associate_blkg_from_css - associate a bio with a specified css\n+ * bio_associate_blkcg_from_css - associate a bio with a specified css\n * @bio: target bio\n * @css: target css\n \n- Associate @bio with the blkg found by combining the css's blkg and the\n- * request_queue of the @bio. An association failure is handled by walking up\n- * the blkg tree. Therefore, the blkg associated can be anything between @blkg\n- * and q-\u003eroot_blkg. This situation only happens when a cgroup is dying and\n- * then the remaining bios will spill to the closest alive blkg.\n+ * Associate @bio with the blkcg found from @css. The queue-local blkg is\n+ * created and pinned by bio_blkg() when blkcg policies need it.\n \n- A reference will be taken on the blkg and will be released when @bio is\n+ * A reference will be taken on the blkcg and will be released when @bio is\n * freed.\n /\n-void bio_associate_blkg_from_css(struct bio bio,\n+void bio_associate_blkcg_from_css(struct bio bio,\n \t\t\t\t struct cgroup_subsys_state css)\n {\n-\tif (bio-\u003ebi_blkg)\n-\t\tblkg_put(bio-\u003ebi_blkg);\n+\tstruct blkcg blkcg;\n \n-\tif (css \u0026\u0026 css-\u003eparent) {\n-\t\tbio-\u003ebi_blkg = blkg_tryget_closest(bio, css);\n-\t} else {\n-\t\tblkg_get(bdev_get_queue(bio-\u003ebi_bdev)-\u003eroot_blkg);\n-\t\tbio-\u003ebi_blkg = bdev_get_queue(bio-\u003ebi_bdev)-\u003eroot_blkg;\n-\t}\n+\tif (!css \|\| !css-\u003eparent)\n+\t\tcss = \u0026blkcg_root.css;\n+\n+\tblkcg = css_to_blkcg(css);\n+\tif (bio_blkcg(bio) == blkcg)\n+\t\treturn;\n+\n+\tcss_get(css);\n+\tbio_clear_blkcg(bio);\n+\tbio-\u003ebi_blkcg = blkcg;\n }\n-EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);\n+EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css);\n \n /\n- bio_associate_blkg - associate a bio with a blkg\n+ * bio_associate_blkcg - associate a bio with a blkcg\n * @bio: target bio\n \n- Associate @bio with the blkg found from the bio's css and request_queue.\n- * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is\n- * already associated, the css is reused and association redone as the\n- * request_queue may have changed.\n+ * Associate @bio with the blkcg found from the bio's css. If a blkcg is\n+ * already associated, keep it as blkcg association is not queue-local.\n /\n-void bio_associate_blkg(struct bio bio)\n+void bio_associate_blkcg(struct bio bio)\n {\n \tstruct cgroup_subsys_state css;\n \n \tif (blk_op_is_passthrough(bio-\u003ebi_opf))\n \t\treturn;\n \n-\tif (bio-\u003ebi_blkg) {\n-\t\tcss = bio_blkcg_css(bio);\n-\t\tbio_associate_blkg_from_css(bio, css);\n-\t} else {\n-\t\trcu_read_lock();\n-\t\tcss = blkcg_css();\n-\t\tif (!css_tryget_online(css))\n-\t\t\tcss = NULL;\n-\t\trcu_read_unlock();\n+\tif (bio_blkcg(bio))\n+\t\treturn;\n \n-\t\tbio_associate_blkg_from_css(bio, css);\n-\t\tif (css)\n-\t\t\tcss_put(css);\n-\t}\n+\trcu_read_lock();\n+\tcss = blkcg_css();\n+\tif (!css_tryget_online(css))\n+\t\tcss = NULL;\n+\trcu_read_unlock();\n+\n+\tbio_associate_blkcg_from_css(bio, css);\n+\tif (css)\n+\t\tcss_put(css);\n }\n-EXPORT_SYMBOL_GPL(bio_associate_blkg);\n+EXPORT_SYMBOL_GPL(bio_associate_blkcg);\n \n /*\n- bio_clone_blkg_association - clone blkg association from src to dst bio\n+ * bio_clone_blkcg_association - clone blkcg association from src to dst bio\n * @dst: destination bio\n * @src: source bio\n /\n-void bio_clone_blkg_association(struct bio dst, struct bio src)\n+void bio_clone_blkcg_association(struct bio dst, struct bio src)\n {\n-\tif (src-\u003ebi_blkg)\n-\t\tbio_associate_blkg_from_css(dst, bio_blkcg_css(src));\n+\tif (bio_blkcg(src))\n+\t\tbio_associate_blkcg_from_css(dst, bio_blkcg_css(src));\n }\n-EXPORT_SYMBOL_GPL(bio_clone_blkg_association);\n+EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);\n \n static int blk_cgroup_io_type(struct bio bio)\n {\n@@ -2181,20 +2231,27 @@ static int blk_cgroup_io_type(struct bio bio)\n \n void blk_cgroup_bio_start(struct bio bio)\n {\n-\tstruct blkcg blkcg = bio-\u003ebi_blkg-\u003eblkcg;\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n+\tstruct blkcg_gq blkg;\n \tint rwd = blk_cgroup_io_type(bio), cpu;\n \tstruct blkg_iostat_set bis;\n \tunsigned long flags;\n \n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys))\n \t\treturn;\n+\tif (!blkcg)\n+\t\treturn;\n \n \t/* Root-level stats are sourced from system-wide IO stats /\n \tif (!cgroup_parent(blkcg-\u003ecss.cgroup))\n \t\treturn;\n \n+\tblkg = bio_blkg_lookup(bio);\n+\tif (!blkg)\n+\t\treturn;\n+\n \tcpu = get_cpu();\n-\tbis = per_cpu_ptr(bio-\u003ebi_blkg-\u003eiostat_cpu, cpu);\n+\tbis = per_cpu_ptr(blkg-\u003eiostat_cpu, cpu);\n \tflags = u64_stats_update_begin_irqsave(\u0026bis-\u003esync);\n \n \t/\ndiff --git a/block/blk-cgroup.h b/block/blk-cgroup.h\nindex 615390f751aa2..b457c2b4ac7c8 100644\n--- a/block/blk-cgroup.h\n+++ b/block/blk-cgroup.h\n@@ -73,14 +73,7 @@ struct blkcg_gq {\n \tstruct blkg_iostat_set\t\tiostat;\n \n \tstruct blkg_policy_data\t\tpd[BLKCG_MAX_POLS];\n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tspinlock_t\t\t\tasync_bio_lock;\n-\tstruct bio_list\t\t\tasync_bios;\n-#endif\n-\tunion {\n-\t\tstruct work_struct\tasync_bio_work;\n-\t\tstruct work_struct\tfree_work;\n-\t};\n+\tstruct work_struct\t\tfree_work;\n \n \tatomic_t\t\t\tuse_delay;\n \tatomic64_t\t\t\tdelay_nsec;\n@@ -111,6 +104,11 @@ struct blkcg {\n \t /\n \tstruct llist_head __percpu\tlhead;\n \n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tspinlock_t\t\t\tasync_bio_lock;\n+\tstruct bio_list\t\t\tasync_bios;\n+\tstruct work_struct\t\tasync_bio_work;\n+#endif\n #ifdef CONFIG_BLK_CGROUP_FC_APPID\n \tchar fc_app_id[FC_APPID_LEN];\n #endif\n@@ -124,6 +122,11 @@ static inline struct blkcg css_to_blkcg(struct cgroup_subsys_state css)\n \treturn css ? container_of(css, struct blkcg, css) : NULL;\n }\n \n+static inline struct blkcg bio_blkcg(struct bio bio)\n+{\n+\treturn bio-\u003ebi_blkcg;\n+}\n+\n /\n * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a\n * request_queue (q). This is used by blkcg policies which need to track\n@@ -276,6 +279,9 @@ static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg,\n \treturn blkg;\n }\n \n+struct blkcg_gq bio_blkg_lookup(struct bio bio);\n+struct blkcg_gq bio_blkg(struct bio bio);\n+\n /*\n blkg_to_pd - get policy private data\n * @blkg: blkg of interest\n@@ -343,6 +349,18 @@ static inline void blkg_put(struct blkcg_gq blkg)\n \tpercpu_ref_put(\u0026blkg-\u003erefcnt);\n }\n \n+static inline void bio_clear_blkcg(struct bio bio)\n+{\n+\tstruct blkcg blkcg = bio_blkcg(bio);\n+\n+\tbio_put_blkg_ref(bio);\n+\n+\tif (blkcg) {\n+\t\tcss_put(\u0026blkcg-\u003ecss);\n+\t\tbio-\u003ebi_blkcg = NULL;\n+\t}\n+}\n+\n /\n blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants\n * @d_blkg: loop cursor pointing to the current descendant\n@@ -455,7 +473,7 @@ static inline void blkcg_clear_delay(struct blkcg_gq blkg)\n /\n static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio)\n {\n-\treturn rq-\u003ebio-\u003ebi_blkg == bio-\u003ebi_blkg \u0026\u0026\n+\treturn bio_blkcg(rq-\u003ebio) == bio_blkcg(bio) \u0026\u0026\n \t\tbio_issue_as_root_blkg(rq-\u003ebio) == bio_issue_as_root_blkg(bio);\n }\n \n@@ -481,6 +499,9 @@ struct blkcg_policy {\n struct blkcg {\n };\n \n+static inline struct blkcg bio_blkcg(struct bio bio) { return NULL; }\n+static inline struct blkcg_gq bio_blkg_lookup(struct bio bio) { return NULL; }\n+static inline struct blkcg_gq bio_blkg(struct bio bio) { return NULL; }\n static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg, void key) { return NULL; }\n static inline void blkg_init_queue(struct request_queue q) { }\n static inline int blkcg_init_disk(struct gendisk disk) { return 0; }\n@@ -497,6 +518,7 @@ static inline struct blkg_policy_data blkg_to_pd(struct blkcg_gq blkg,\n static inline struct blkcg_gq pd_to_blkg(struct blkg_policy_data pd) { return NULL; }\n static inline void blkg_get(struct blkcg_gq blkg) { }\n static inline void blkg_put(struct blkcg_gq blkg) { }\n+static inline void bio_clear_blkcg(struct bio bio) { }\n static inline void blk_cgroup_bio_start(struct bio bio) { }\n static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio) { return true; }\n \ndiff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c\nindex 2a5c52ab74b4c..5ef4baab444bb 100644\n--- a/block/blk-crypto-fallback.c\n+++ b/block/blk-crypto-fallback.c\n@@ -187,7 +187,7 @@ static struct bio blk_crypto_alloc_enc_bio(struct bio bio_src,\n \tbio-\u003ebi_write_hint\t= bio_src-\u003ebi_write_hint;\n \tbio-\u003ebi_write_stream\t= bio_src-\u003ebi_write_stream;\n \tbio-\u003ebi_iter.bi_sector\t= bio_src-\u003ebi_iter.bi_sector;\n-\tbio_clone_blkg_association(bio, bio_src);\n+\tbio_clone_blkcg_association(bio, bio_src);\n \n \t/\n \t * Move page array up in the allocated memory for the bio vecs as far as\ndiff --git a/block/blk-iocost.c b/block/blk-iocost.c\nindex 8b2aeba2e1e39..62ffd759bb954 100644\n--- a/block/blk-iocost.c\n+++ b/block/blk-iocost.c\n@@ -2686,7 +2686,7 @@ iocg_handle_over_budget(struct rq_qos rqos, struct ioc_gq iocg,\n \n static void ioc_rqos_throttle(struct rq_qos rqos, struct bio bio)\n {\n-\tstruct blkcg_gq blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq blkg = bio_blkg(bio);\n \tstruct ioc ioc = rqos_to_ioc(rqos);\n \tstruct ioc_gq iocg = blkg_to_iocg(blkg);\n \tstruct ioc_now now;\n@@ -2775,7 +2775,7 @@ static void ioc_rqos_throttle(struct rq_qos rqos, struct bio bio)\n static void ioc_rqos_merge(struct rq_qos rqos, struct request rq,\n \t\t\t struct bio bio)\n {\n-\tstruct ioc_gq iocg = blkg_to_iocg(bio-\u003ebi_blkg);\n+\tstruct ioc_gq iocg = blkg_to_iocg(bio_blkg_lookup(bio));\n \tstruct ioc ioc = rqos_to_ioc(rqos);\n \tsector_t bio_end = bio_end_sector(bio);\n \tstruct ioc_now now;\n@@ -2833,9 +2833,13 @@ static void ioc_rqos_merge(struct rq_qos rqos, struct request rq,\n \n static void ioc_rqos_done_bio(struct rq_qos rqos, struct bio bio)\n {\n-\tstruct ioc_gq iocg = blkg_to_iocg(bio-\u003ebi_blkg);\n+\tstruct ioc_gq iocg;\n+\n+\tif (!bio-\u003ebi_iocost_cost)\n+\t\treturn;\n \n-\tif (iocg \u0026\u0026 bio-\u003ebi_iocost_cost)\n+\tiocg = blkg_to_iocg(bio_blkg_lookup(bio));\n+\tif (iocg)\n \t\tatomic64_add(bio-\u003ebi_iocost_cost, \u0026iocg-\u003edone_vtime);\n }\n \ndiff --git a/block/blk-iolatency.c b/block/blk-iolatency.c\nindex cef02b6c5fa91..7ad18a538d7e2 100644\n--- a/block/blk-iolatency.c\n+++ b/block/blk-iolatency.c\n@@ -463,7 +463,7 @@ static void check_scale_change(struct iolatency_grp iolat)\n static void blkcg_iolatency_throttle(struct rq_qos rqos, struct bio bio)\n {\n \tstruct blk_iolatency blkiolat = BLKIOLATENCY(rqos);\n-\tstruct blkcg_gq blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq blkg = bio_blkg(bio);\n \tbool issue_as_root = bio_issue_as_root_blkg(bio);\n \n \tif (!blkiolat-\u003eenabled)\n@@ -590,11 +590,14 @@ static void blkcg_iolatency_done_bio(struct rq_qos rqos, struct bio bio)\n \tbool issue_as_root = bio_issue_as_root_blkg(bio);\n \tint inflight = 0;\n \n-\tblkg = bio-\u003ebi_blkg;\n-\tif (!blkg \|\| !bio_flagged(bio, BIO_QOS_THROTTLED))\n+\tif (!bio_flagged(bio, BIO_QOS_THROTTLED))\n \t\treturn;\n \n-\tiolat = blkg_to_lat(bio-\u003ebi_blkg);\n+\tblkg = bio_blkg_lookup(bio);\n+\tif (!blkg)\n+\t\treturn;\n+\n+\tiolat = blkg_to_lat(blkg);\n \tif (!iolat)\n \t\treturn;\n \ndiff --git a/block/blk-ioprio.c b/block/blk-ioprio.c\nindex 8fa8bca350629..5e3f8e49550da 100644\n--- a/block/blk-ioprio.c\n+++ b/block/blk-ioprio.c\n@@ -132,7 +132,7 @@ static struct blkcg_policy ioprio_policy = {\n \n void blkcg_set_ioprio(struct bio bio)\n {\n-\tstruct ioprio_blkcg blkcg = blkcg_to_ioprio_blkcg(bio-\u003ebi_blkg-\u003eblkcg);\n+\tstruct ioprio_blkcg blkcg = blkcg_to_ioprio_blkcg(bio_blkcg(bio));\n \tu16 prio;\n \n \tif (!blkcg \|\| blkcg-\u003eprio_policy == POLICY_NO_CHANGE)\ndiff --git a/block/blk-throttle.c b/block/blk-throttle.c\nindex ffc3b70065d4b..3828c38579002 100644\n--- a/block/blk-throttle.c\n+++ b/block/blk-throttle.c\n@@ -1792,7 +1792,7 @@ static bool tg_within_limit(struct throtl_grp tg, struct bio bio, bool rw)\n bool __blk_throtl_bio(struct bio bio)\n {\n \tstruct request_queue q = bdev_get_queue(bio-\u003ebi_bdev);\n-\tstruct blkcg_gq blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq blkg = bio_blkg(bio);\n \tstruct throtl_qnode qn = NULL;\n \tstruct throtl_grp tg = blkg_to_tg(blkg);\n \tstruct throtl_service_queue sq;\ndiff --git a/block/blk-throttle.h b/block/blk-throttle.h\nindex 9d7a42c039a15..609a126c7ccb2 100644\n--- a/block/blk-throttle.h\n+++ b/block/blk-throttle.h\n@@ -173,7 +173,7 @@ static inline bool blk_should_throtl(struct bio bio)\n \tif (!blk_throtl_activated(bio-\u003ebi_bdev-\u003ebd_queue))\n \t\treturn false;\n \n-\ttg = blkg_to_tg(bio-\u003ebi_blkg);\n+\ttg = blkg_to_tg(bio_blkg(bio));\n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {\n \t\tif (!bio_flagged(bio, BIO_CGROUP_ACCT)) {\n \t\t\tbio_set_flag(bio, BIO_CGROUP_ACCT);\ndiff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c\nindex 3fa3b13a410f4..c0f945b8d9413 100644\n--- a/drivers/md/bcache/request.c\n+++ b/drivers/md/bcache/request.c\n@@ -848,7 +848,7 @@ static CLOSURE_CALLBACK(cached_dev_read_done)\n \t\ts-\u003eiop.bio-\u003ebi_iter.bi_sector =\n \t\t\ts-\u003ecache_miss-\u003ebi_iter.bi_sector;\n \t\ts-\u003eiop.bio-\u003ebi_iter.bi_size = s-\u003einsert_bio_sectors \u003c\u003c 9;\n-\t\tbio_clone_blkg_association(s-\u003eiop.bio, s-\u003ecache_miss);\n+\t\tbio_clone_blkcg_association(s-\u003eiop.bio, s-\u003ecache_miss);\n \t\tbch_bio_map(s-\u003eiop.bio, NULL);\n \n \t\tbio_copy_data(s-\u003ecache_miss, s-\u003eiop.bio);\ndiff --git a/drivers/md/dm.c b/drivers/md/dm.c\nindex d413bfaf35278..cd68eec77f5a1 100644\n--- a/drivers/md/dm.c\n+++ b/drivers/md/dm.c\n@@ -1373,7 +1373,7 @@ void dm_submit_bio_remap(struct bio clone, struct bio tgt_clone)\n \tif (!tgt_clone)\n \t\ttgt_clone = clone;\n \n-\tbio_clone_blkg_association(tgt_clone, io-\u003eorig_bio);\n+\tbio_clone_blkcg_association(tgt_clone, io-\u003eorig_bio);\n \n \t/\n \t * Account io-\u003eorigin_bio to DM dev on behalf of target\ndiff --git a/drivers/md/md.c b/drivers/md/md.c\nindex d1465bcd86c81..af55f8efa46bc 100644\n--- a/drivers/md/md.c\n+++ b/drivers/md/md.c\n@@ -9355,7 +9355,7 @@ void md_submit_discard_bio(struct mddev mddev, struct md_rdev rdev,\n \t\treturn;\n \n \tbio_chain(discard_bio, bio);\n-\tbio_clone_blkg_association(discard_bio, bio);\n+\tbio_clone_blkcg_association(discard_bio, bio);\n \tmddev_trace_remap(mddev, discard_bio, bio-\u003ebi_iter.bi_sector);\n \tsubmit_bio_noacct(discard_bio);\n }\ndiff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c\nindex 4176046627beb..54e4adb0ccb7d 100644\n--- a/drivers/nvdimm/nd_virtio.c\n+++ b/drivers/nvdimm/nd_virtio.c\n@@ -121,7 +121,7 @@ int async_pmem_flush(struct nd_region nd_region, struct bio bio)\n \n \t\tif (!child)\n \t\t\treturn -ENOMEM;\n-\t\tbio_clone_blkg_association(child, bio);\n+\t\tbio_clone_blkcg_association(child, bio);\n \t\tchild-\u003ebi_iter.bi_sector = -1;\n \t\tbio_chain(child, bio);\n \t\tsubmit_bio(child);\ndiff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c\nindex 6dabe73ad790d..6512dbd9516fc 100644\n--- a/fs/gfs2/lops.c\n+++ b/fs/gfs2/lops.c\n@@ -484,7 +484,7 @@ static struct bio gfs2_chain_bio(struct bio prev, unsigned int nr_iovecs,\n \tstruct bio new;\n \n \tnew = bio_alloc(prev-\u003ebi_bdev, nr_iovecs, opf, GFP_NOIO);\n-\tbio_clone_blkg_association(new, prev);\n+\tbio_clone_blkcg_association(new, prev);\n \tnew-\u003ebi_iter.bi_sector = sector;\n \tbio_chain(new, prev);\n \tsubmit_bio(prev);\n@@ -1114,4 +1114,3 @@ const struct gfs2_log_operations gfs2_log_ops[] = {\n \t\u0026gfs2_revoke_lops,\n \tNULL,\n };\n-\ndiff --git a/include/linux/bio.h b/include/linux/bio.h\nindex 8f33f717b14f5..e5799fdf431d2 100644\n--- a/include/linux/bio.h\n+++ b/include/linux/bio.h\n@@ -503,18 +503,20 @@ static inline void bio_release_pages(struct bio bio, bool mark_dirty)\n \tdisk_devt((bio)-\u003ebi_bdev-\u003ebd_disk)\n \n #ifdef CONFIG_BLK_CGROUP\n-void bio_associate_blkg(struct bio bio);\n-void bio_associate_blkg_from_css(struct bio bio,\n+void bio_associate_blkcg(struct bio bio);\n+void bio_associate_blkcg_from_css(struct bio bio,\n \t\t\t\t struct cgroup_subsys_state css);\n-void bio_clone_blkg_association(struct bio dst, struct bio src);\n+void bio_clone_blkcg_association(struct bio dst, struct bio src);\n+void bio_put_blkg_ref(struct bio bio);\n void blkcg_punt_bio_submit(struct bio bio);\n #else\t/* CONFIG_BLK_CGROUP /\n-static inline void bio_associate_blkg(struct bio bio) { }\n-static inline void bio_associate_blkg_from_css(struct bio bio,\n+static inline void bio_associate_blkcg(struct bio bio) { }\n+static inline void bio_associate_blkcg_from_css(struct bio bio,\n \t\t\t\t\t struct cgroup_subsys_state css)\n { }\n-static inline void bio_clone_blkg_association(struct bio dst,\n+static inline void bio_clone_blkcg_association(struct bio dst,\n \t\t\t\t\t struct bio src) { }\n+static inline void bio_put_blkg_ref(struct bio bio) { }\n static inline void blkcg_punt_bio_submit(struct bio bio)\n {\n \tsubmit_bio(bio);\n@@ -524,10 +526,12 @@ static inline void blkcg_punt_bio_submit(struct bio bio)\n static inline void bio_set_dev(struct bio bio, struct block_device bdev)\n {\n \tbio_clear_flag(bio, BIO_REMAPPED);\n-\tif (bio-\u003ebi_bdev != bdev)\n+\tif (bio-\u003ebi_bdev != bdev) {\n+\t\tbio_put_blkg_ref(bio);\n \t\tbio_clear_flag(bio, BIO_BPS_THROTTLED);\n+\t}\n \tbio-\u003ebi_bdev = bdev;\n-\tbio_associate_blkg(bio);\n+\tbio_associate_blkcg(bio);\n }\n \n /\ndiff --git a/include/linux/blk_types.h b/include/linux/blk_types.h\nindex 8808ee76e73c0..5f95c2e0e90b0 100644\n--- a/include/linux/blk_types.h\n+++ b/include/linux/blk_types.h\n@@ -246,12 +246,10 @@ struct bio {\n \tvoid\t\t\tbi_private;\n #ifdef CONFIG_BLK_CGROUP\n \t/\n-\t Represents the association of the css and request_queue for the bio.\n-\t * If a bio goes direct to device, it will not have a blkg as it will\n-\t * not have a request_queue associated with it. The reference is put\n-\t * on release of the bio.\n+\t * Represents the blkcg css association for the bio. The reference is\n+\t * put on release of the bio.\n \t /\n-\tstruct blkcg_gq\t\tbi_blkg;\n+\tstruct blkcg\t\tbi_blkcg;\n \t/ Time that this bio was issued. /\n \tu64\t\t\tissue_time_ns;\n #ifdef CONFIG_BLK_CGROUP_IOCOST\n@@ -309,6 +307,7 @@ enum {\n \tBIO_TRACE_COMPLETION,\t/ bio_endio() should trace the final completion\n \t\t\t\t * of this bio. /\n \tBIO_CGROUP_ACCT,\t/ has been accounted to a cgroup /\n+\tBIO_BLKG_REF,\t\t/ bio pins the associated blkg /\n \tBIO_QOS_THROTTLED,\t/ bio went through rq_qos throttle path /\n \t/\n \t * This bio has completed bps throttling at the single tg granularity,\ndiff --git a/include/linux/writeback.h b/include/linux/writeback.h\nindex 62552a2ce5b9e..4f869fe9cc90f 100644\n--- a/include/linux/writeback.h\n+++ b/include/linux/writeback.h\n@@ -262,7 +262,7 @@ static inline void wbc_init_bio(struct writeback_control wbc, struct bio bio)\n \t * regular writeback instead of writing things out itself.\n \t /\n \tif (wbc-\u003ewb)\n-\t\tbio_associate_blkg_from_css(bio, wbc-\u003ewb-\u003eblkcg_css);\n+\t\tbio_associate_blkcg_from_css(bio, wbc-\u003ewb-\u003eblkcg_css);\n }\n \n void inode_switch_wbs_work_fn(struct work_struct work);\ndiff --git a/mm/page_io.c b/mm/page_io.c\nindex b23f494fcc83d..112e504756055 100644\n--- a/mm/page_io.c\n+++ b/mm/page_io.c\n@@ -316,7 +316,7 @@ static inline void count_swpout_vm_event(struct folio folio)\n }\n \n #if defined(CONFIG_MEMCG) \u0026\u0026 defined(CONFIG_BLK_CGROUP)\n-static void bio_associate_blkg_from_page(struct bio bio, struct folio folio)\n+static void bio_associate_blkcg_from_page(struct bio bio, struct folio folio)\n {\n \tstruct cgroup_subsys_state css;\n \tstruct mem_cgroup memcg;\n@@ -331,12 +331,12 @@ static void bio_associate_blkg_from_page(struct bio bio, struct folio folio)\n \t\tcss = NULL;\n \trcu_read_unlock();\n \n-\tbio_associate_blkg_from_css(bio, css);\n+\tbio_associate_blkcg_from_css(bio, css);\n \tif (css)\n \t\tcss_put(css);\n }\n #else\n-#define bio_associate_blkg_from_page(bio, folio)\t\tdo { } while (0)\n+#define bio_associate_blkcg_from_page(bio, folio)\tdo { } while (0)\n #endif / CONFIG_MEMCG \u0026\u0026 CONFIG_BLK_CGROUP /\n \n struct swap_iocb {\n@@ -436,7 +436,7 @@ static void swap_writepage_bdev_sync(struct folio folio,\n \tbio.bi_iter.bi_sector = swap_folio_sector(folio);\n \tbio_add_folio_nofail(\u0026bio, folio, folio_size(folio), 0);\n \n-\tbio_associate_blkg_from_page(\u0026bio, folio);\n+\tbio_associate_blkcg_from_page(\u0026bio, folio);\n \tcount_swpout_vm_event(folio);\n \n \tfolio_start_writeback(folio);\n@@ -456,7 +456,7 @@ static void swap_writepage_bdev_async(struct folio *folio,\n \tbio-\u003ebi_end_io = end_swap_bio_write;\n \tbio_add_folio_nofail(bio, folio, folio_size(folio), 0);\n \n-\tbio_associate_blkg_from_page(bio, folio);\n+\tbio_associate_blkcg_from_page(bio, folio);\n \tcount_swpout_vm_event(folio);\n \tfolio_start_writeback(folio);\n \tfolio_unlock(folio);\n" }
2/1	2026/08/04 07:16	agent	patch-evaluator	7m Model: best-expensive Args: null Results: { "EnableConfigs": [ "BLK_CGROUP", "BLK_CGROUP_IOLATENCY", "BLK_CGROUP_IOCOST", "BLK_CGROUP_IOPRIO", "IOSCHED_BFQ", "BFQ_GROUP_IOSCHED", "NVME_FC", "BLK_CGROUP_FC_APPID", "BTRFS_FS", "MEMCG", "BLK_DEV_THROTTLING", "BLK_DEV_MD", "BCACHE", "BLK_DEV_DM", "BLK_INLINE_ENCRYPTION", "BLK_INLINE_ENCRYPTION_FALLBACK", "GFS2_FS", "BLK_DEV_PMEM", "VIRTIO_PMEM" ], "FocusSymbols": [ "bio_blkg_lookup", "bio_blkg", "bio_associate_blkcg_from_css", "bio_associate_blkcg", "bio_clone_blkcg_association", "bio_put_blkg_ref", "blkcg_punt_bio_submit", "bfq_bio_bfqg", "blkcg_get_fc_appid", "blkcg_set_ioprio", "__blk_throtl_bio", "bfqg_stats_update_legacy_io", "blk_cgroup_bio_start" ], "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer. Your job is to review a provided patch series and determine if it makes functional changes to the kernel that should be fuzzed. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your code access tools to examine the actual source code and confirm any assumptions. Return WorthFuzzing=false if the patch only contains: - Modifications to Documentation/, Kconfig files, or code comments. - Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints. - Changes to numeric constants or macros that do not functionally alter execution flow. - Code paths that are impossible to reach in virtualized environments like GCE or QEMU, even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim). - Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU. - Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove) that are executed only during PCI hot-unplug or sysfs driver unbind operations. If it modifies reachable core kernel logic, drivers, or architectures, use your code search tools to verify the code can be executed, then return WorthFuzzing=true. When returning WorthFuzzing=true, you MUST ALSO: 1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols. Avoid listing generic hot-path functions to prevent skewed test distributions. Prefer non-static, non-inlined API entrypoint functions over internal static helper functions (which are inlined by the compiler and do not have distinct symbol addresses). 2. Identify any specific CONFIG_ options required to properly test this new/modified feature. Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions. Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs output array, and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: For your convenience, here is the diff of the changes: commit 37ab22cb5f20111358288fbe1554a0d2e13b1a8a Author: syz-cluster <triage@syzkaller.com> Date: Tue Aug 4 07:16:16 2026 +0000 syz-cluster: applied patch under review diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 14b8c571c0d14..bbd79931d5ab5 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -3235,7 +3235,7 @@ the configuration, the bio may be executed at a lower priority and if the writeback session is holding shared resources, e.g. a journal entry, may lead to priority inversion. There is no one easy solution for the problem. Filesystems can try to work around specific problem -cases by skipping wbc_init_bio() and using bio_associate_blkg() +cases by skipping wbc_init_bio() and using bio_associate_blkcg() directly. diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index e82ff03bda02e..3ac3b4c054026 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -363,11 +363,13 @@ void bfqg_and_blkg_put(struct bfq_group bfqg) void bfqg_stats_update_legacy_io(struct request_queue q, struct request rq) { - struct bfq_group bfqg = blkg_to_bfqg(rq->bio->bi_blkg); + struct blkcg_gq blkg = bio_blkg_lookup(rq->bio); + struct bfq_group bfqg; - if (!bfqg) + if (!blkg) return; + bfqg = blkg_to_bfqg(blkg); blkg_rwstat_add(&bfqg->stats.bytes, rq->cmd_flags, blk_rq_bytes(rq)); blkg_rwstat_add(&bfqg->stats.ios, rq->cmd_flags, 1); } @@ -606,7 +608,7 @@ static void bfq_link_bfqg(struct bfq_data bfqd, struct bfq_group bfqg) struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio) { - struct blkcg_gq blkg = bio->bi_blkg; + struct blkcg_gq blkg = bio_blkg_lookup(bio); struct bfq_group bfqg; while (blkg) { @@ -614,14 +616,16 @@ struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio) blkg = blkg->parent; continue; } + bfqg = blkg_to_bfqg(blkg); if (bfqg->pd.online) { - bio_associate_blkg_from_css(bio, &blkg->blkcg->css); + bio_associate_blkcg_from_css(bio, &blkg->blkcg->css); return bfqg; } blkg = blkg->parent; } - bio_associate_blkg_from_css(bio, + + bio_associate_blkcg_from_css(bio, &bfqg_to_blkg(bfqd->root_group)->blkcg->css); return bfqd->root_group; } diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 0f75301b3115f..3d51d743552cb 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -128,6 +128,7 @@ #include "elevator.h" #include "blk.h" +#include "blk-cgroup.h" #include "blk-mq.h" #include "blk-mq-sched.h" #include "bfq-iosched.h" @@ -2452,15 +2453,15 @@ static bool bfq_bio_merge(struct request_queue q, struct bio bio, struct request free = NULL; bool ret; +#ifdef CONFIG_BFQ_GROUP_IOSCHED + if (bic && bio_blkg_lookup(bio) == NULL) + return false; +#endif + spin_lock_irq(&bfqd->lock); if (bic) { - /* - * Make sure cgroup info is uptodate for current process before - * considering the merge. - / bfq_bic_update_cgroup(bic, bio); - bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf), bfq_actuator_index(bfqd, bio)); } else { @@ -6245,6 +6246,13 @@ static void bfq_insert_request(struct blk_mq_hw_ctx hctx, struct request rq, LIST_HEAD(free); #ifdef CONFIG_BFQ_GROUP_IOSCHED + / + * Pin the blkg used to look up bfqg. If this is the first IO for + * the blkcg on this queue, create the bfqg before holding bfqd->lock. + / + if (rq->bio && !bio_flagged(rq->bio, BIO_BLKG_REF)) + bio_blkg(rq->bio); + if (!cgroup_subsys_on_dfl(io_cgrp_subsys) && rq->bio) bfqg_stats_update_legacy_io(q, rq); #endif diff --git a/block/bio.c b/block/bio.c index 6a2f6fc3413e8..db33c993c2964 100644 --- a/block/bio.c +++ b/block/bio.c @@ -179,12 +179,7 @@ static inline gfp_t try_alloc_gfp(gfp_t gfp) void bio_uninit(struct bio bio) { -#ifdef CONFIG_BLK_CGROUP - if (bio->bi_blkg) { - blkg_put(bio->bi_blkg); - bio->bi_blkg = NULL; - } -#endif + bio_clear_blkcg(bio); if (bio_integrity(bio)) bio_integrity_free(bio); @@ -233,10 +228,10 @@ void bio_init(struct bio bio, struct block_device bdev, struct bio_vec table, bio->bi_end_io = NULL; bio->bi_private = NULL; #ifdef CONFIG_BLK_CGROUP - bio->bi_blkg = NULL; + bio->bi_blkcg = NULL; bio->issue_time_ns = 0; if (bdev) - bio_associate_blkg(bio); + bio_associate_blkcg(bio); #ifdef CONFIG_BLK_CGROUP_IOCOST bio->bi_iocost_cost = 0; #endif @@ -281,7 +276,7 @@ void bio_reset(struct bio bio, struct block_device bdev, blk_opf_t opf) bio->bi_io_vec = bv; bio->bi_bdev = bdev; if (bio->bi_bdev) - bio_associate_blkg(bio); + bio_associate_blkcg(bio); bio->bi_opf = opf; } EXPORT_SYMBOL(bio_reset); @@ -865,7 +860,7 @@ static int __bio_clone(struct bio bio, struct bio bio_src, gfp_t gfp) if (bio->bi_bdev == bio_src->bi_bdev && bio_flagged(bio_src, BIO_REMAPPED)) bio_set_flag(bio, BIO_REMAPPED); - bio_clone_blkg_association(bio, bio_src); + bio_clone_blkcg_association(bio, bio_src); } if (bio_crypt_clone(bio, bio_src, gfp) < 0) @@ -1803,17 +1798,12 @@ void bio_endio(struct bio bio) goto again; } -#ifdef CONFIG_BLK_CGROUP /* * Release cgroup info. We shouldn't have to do this here, but quite * a few callers of bio_init fail to call bio_uninit, so we cover up * for that here at least for now. / - if (bio->bi_blkg) { - blkg_put(bio->bi_blkg); - bio->bi_blkg = NULL; - } -#endif + bio_clear_blkcg(bio); if (bio->bi_end_io) bio->bi_end_io(bio); diff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c index 3ec21333f393b..7589c62099898 100644 --- a/block/blk-cgroup-fc-appid.c +++ b/block/blk-cgroup-fc-appid.c @@ -50,8 +50,14 @@ EXPORT_SYMBOL_GPL(blkcg_set_fc_appid); / char blkcg_get_fc_appid(struct bio bio) { - if (!bio->bi_blkg \|\| bio->bi_blkg->blkcg->fc_app_id[0] == '\0') + struct blkcg blkcg = bio_blkcg(bio); + + if (!blkcg) + return NULL; + + if (blkcg->fc_app_id[0] == '\0') return NULL; - return bio->bi_blkg->blkcg->fc_app_id; + + return blkcg->fc_app_id; } EXPORT_SYMBOL_GPL(blkcg_get_fc_appid); diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index d9676126c5b5d..a70f92f1541b1 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -170,10 +170,6 @@ static void __blkg_release(struct rcu_head rcu) { struct blkcg_gq blkg = container_of(rcu, struct blkcg_gq, rcu_head); -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - WARN_ON(!bio_list_empty(&blkg->async_bios)); -#endif - blkg_free(blkg); } @@ -206,19 +202,18 @@ static void blkg_release(struct percpu_ref ref) #ifdef CONFIG_BLK_CGROUP_PUNT_BIO static struct workqueue_struct blkcg_punt_bio_wq; -static void blkg_async_bio_workfn(struct work_struct work) +static void blkcg_async_bio_workfn(struct work_struct work) { - struct blkcg_gq blkg = container_of(work, struct blkcg_gq, - async_bio_work); + struct blkcg blkcg = container_of(work, struct blkcg, async_bio_work); struct bio_list bios = BIO_EMPTY_LIST; struct bio bio; struct blk_plug plug; bool need_plug = false; - /* as long as there are pending bios, @blkg can't go away / - spin_lock(&blkg->async_bio_lock); - bio_list_merge_init(&bios, &blkg->async_bios); - spin_unlock(&blkg->async_bio_lock); + / as long as there are pending bios, @blkcg can't go away / + spin_lock(&blkcg->async_bio_lock); + bio_list_merge_init(&bios, &blkcg->async_bios); + spin_unlock(&blkcg->async_bio_lock); / start plug only when bio_list contains at least 2 bios / if (bios.head && bios.head->bi_next) { @@ -239,15 +234,15 @@ static void blkg_async_bio_workfn(struct work_struct work) / void blkcg_punt_bio_submit(struct bio bio) { - struct blkcg_gq blkg = bio->bi_blkg; + struct blkcg blkcg = bio_blkcg(bio); - if (blkg->parent) { - spin_lock(&blkg->async_bio_lock); - bio_list_add(&blkg->async_bios, bio); - spin_unlock(&blkg->async_bio_lock); - queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work); + if (blkcg && cgroup_parent(blkcg->css.cgroup)) { + spin_lock(&blkcg->async_bio_lock); + bio_list_add(&blkcg->async_bios, bio); + spin_unlock(&blkcg->async_bio_lock); + queue_work(blkcg_punt_bio_wq, &blkcg->async_bio_work); } else { - /* never bounce for the root cgroup / + / Never bounce if there is no non-root blkcg to queue on. / submit_bio(bio); } } @@ -275,9 +270,9 @@ subsys_initcall(blkcg_punt_bio_init); / struct cgroup_subsys_state bio_blkcg_css(struct bio bio) { - if (!bio \|\| !bio->bi_blkg) + if (!bio \|\| !bio_blkcg(bio)) return NULL; - return &bio->bi_blkg->blkcg->css; + return &bio_blkcg(bio)->css; } EXPORT_SYMBOL_GPL(bio_blkcg_css); @@ -325,11 +320,6 @@ static struct blkcg_gq blkg_alloc(struct blkcg blkcg, struct gendisk disk, INIT_LIST_HEAD(&blkg->q_node); blkg->blkcg = blkcg; blkg->iostat.blkg = blkg; -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - spin_lock_init(&blkg->async_bio_lock); - bio_list_init(&blkg->async_bios); - INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn); -#endif u64_stats_init(&blkg->iostat.sync); for_each_possible_cpu(cpu) { @@ -1357,6 +1347,9 @@ static void blkcg_css_free(struct cgroup_subsys_state css) mutex_unlock(&blkcg_pol_mutex); +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + WARN_ON(!bio_list_empty(&blkcg->async_bios)); +#endif free_percpu(blkcg->lhead); kfree(blkcg); } @@ -1406,6 +1399,11 @@ blkcg_css_alloc(struct cgroup_subsys_state parent_css) refcount_set(&blkcg->online_pin, 1); INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT); INIT_HLIST_HEAD(&blkcg->blkg_list); +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + spin_lock_init(&blkcg->async_bio_lock); + bio_list_init(&blkcg->async_bios); + INIT_WORK(&blkcg->async_bio_work, blkcg_async_bio_workfn); +#endif #ifdef CONFIG_CGROUP_WRITEBACK INIT_LIST_HEAD(&blkcg->cgwb_list); #endif @@ -2046,129 +2044,181 @@ void blkcg_add_delay(struct blkcg_gq blkg, u64 now, u64 delta) atomic64_add(delta, &blkg->delay_nsec); } -static inline struct blkcg_gq blkg_lookup_tryget(struct blkcg_gq blkg) +/* + * Return the blkg pinned by @bio through BIO_BLKG_REF. The returned blkg is + * already owned by @bio and no extra reference is acquired. If the pinned + * blkg can't be found, fall back to the root blkg. + / +static struct blkcg_gq bio_pinned_blkg(struct bio bio) { -retry: - if (blkg_tryget(blkg)) - return blkg; + struct request_queue q = bdev_get_queue(bio->bi_bdev); + struct blkcg_gq blkg; - blkg = blkg->parent; - if (blkg) - goto retry; + rcu_read_lock(); + blkg = blkg_lookup(bio_blkcg(bio), q); + rcu_read_unlock(); - return NULL; + if (WARN_ON_ONCE(!blkg)) + return q->root_blkg; + return blkg; } + /* - * blkg_tryget_closest - try and get a blkg ref on the closet blkg + * bio_blkg_lookup - look up a blkg associated with a bio * @bio: target bio - * @css: target css * - * As the failure mode here is to walk up the blkg tree, this ensure that the - * blkg->parent pointers are always valid. This returns the blkg that it ended - * up taking a reference on or %NULL if no reference was taken. + * Look up the queue-local blkg for @bio's current device and blkcg without + * creating a missing blkg. The first successful lookup pins the blkg to @bio; + * later lookups reuse the bio-owned reference. / -static inline struct blkcg_gq blkg_tryget_closest(struct bio bio, - struct cgroup_subsys_state css) +struct blkcg_gq bio_blkg_lookup(struct bio bio) { - struct request_queue q = bio->bi_bdev->bd_queue; - struct blkcg blkcg = css_to_blkcg(css); + struct blkcg blkcg = bio_blkcg(bio); + struct request_queue q; struct blkcg_gq blkg; + if (bio_flagged(bio, BIO_BLKG_REF)) + return bio_pinned_blkg(bio); + + if (!blkcg \|\| !bio->bi_bdev) + return NULL; + + q = bdev_get_queue(bio->bi_bdev); rcu_read_lock(); blkg = blkg_lookup(blkcg, q); - if (likely(blkg)) - blkg = blkg_lookup_tryget(blkg); + if (blkg && blkg_tryget(blkg)) + bio_set_flag(bio, BIO_BLKG_REF); + else + blkg = NULL; rcu_read_unlock(); - if (blkg) - return blkg; + return blkg; +} +EXPORT_SYMBOL_GPL(bio_blkg_lookup); + +/* + * bio_put_blkg_ref - drop the blkg reference pinned by a bio + * @bio: target bio + * + * Drop the bio-owned blkg reference acquired by bio_blkg(), if any. + / +void bio_put_blkg_ref(struct bio bio) +{ + if (bio_flagged(bio, BIO_BLKG_REF)) { + struct blkcg_gq blkg = bio_pinned_blkg(bio); + + blkg_put(blkg); + bio_clear_flag(bio, BIO_BLKG_REF); + } +} +EXPORT_SYMBOL_GPL(bio_put_blkg_ref); + +/* + * bio_blkg - look up the blkg associated with a bio + * @bio: target bio + * + * Look up the queue-local blkg for @bio's current device and blkcg. If this + * is the first policy use of @bio, create the missing blkg hierarchy if + * necessary, pin the exact blkg, and mark @bio so bio_clear_blkcg() can drop + * the reference when the bio completes. + / +struct blkcg_gq bio_blkg(struct bio bio) +{ + struct blkcg blkcg = bio_blkcg(bio); + struct gendisk disk; + struct request_queue q; + struct blkcg_gq blkg; + + if (!blkcg \|\| !bio->bi_bdev) + return NULL; + + if (bio_flagged(bio, BIO_BLKG_REF)) + return bio_pinned_blkg(bio); + + disk = bio->bi_bdev->bd_disk; + q = disk->queue; - / - * Fast path failed, we're probably issuing IO in this cgroup the first - * time, hold lock to create new blkg. - / spin_lock_irq(&q->queue_lock); - blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk); - if (blkg) - blkg = blkg_lookup_tryget(blkg); + blkg = blkg_lookup_create(blkcg, disk); + if (blkg && blkg->blkcg == blkcg && blkg_tryget(blkg)) + bio_set_flag(bio, BIO_BLKG_REF); + else + blkg = NULL; spin_unlock_irq(&q->queue_lock); return blkg; } +EXPORT_SYMBOL_GPL(bio_blkg); /* - * bio_associate_blkg_from_css - associate a bio with a specified css + * bio_associate_blkcg_from_css - associate a bio with a specified css * @bio: target bio * @css: target css * - * Associate @bio with the blkg found by combining the css's blkg and the - * request_queue of the @bio. An association failure is handled by walking up - * the blkg tree. Therefore, the blkg associated can be anything between @blkg - * and q->root_blkg. This situation only happens when a cgroup is dying and - * then the remaining bios will spill to the closest alive blkg. + * Associate @bio with the blkcg found from @css. The queue-local blkg is + * created and pinned by bio_blkg() when blkcg policies need it. * - * A reference will be taken on the blkg and will be released when @bio is + * A reference will be taken on the blkcg and will be released when @bio is * freed. / -void bio_associate_blkg_from_css(struct bio bio, +void bio_associate_blkcg_from_css(struct bio bio, struct cgroup_subsys_state css) { - if (bio->bi_blkg) - blkg_put(bio->bi_blkg); + struct blkcg blkcg; - if (css && css->parent) { - bio->bi_blkg = blkg_tryget_closest(bio, css); - } else { - blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg); - bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg; - } + if (!css \|\| !css->parent) + css = &blkcg_root.css; + + blkcg = css_to_blkcg(css); + if (bio_blkcg(bio) == blkcg) + return; + + css_get(css); + bio_clear_blkcg(bio); + bio->bi_blkcg = blkcg; } -EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); +EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css); /* - * bio_associate_blkg - associate a bio with a blkg + * bio_associate_blkcg - associate a bio with a blkcg * @bio: target bio * - * Associate @bio with the blkg found from the bio's css and request_queue. - * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is - * already associated, the css is reused and association redone as the - * request_queue may have changed. + * Associate @bio with the blkcg found from the bio's css. If a blkcg is + * already associated, keep it as blkcg association is not queue-local. / -void bio_associate_blkg(struct bio bio) +void bio_associate_blkcg(struct bio bio) { struct cgroup_subsys_state css; if (blk_op_is_passthrough(bio->bi_opf)) return; - if (bio->bi_blkg) { - css = bio_blkcg_css(bio); - bio_associate_blkg_from_css(bio, css); - } else { - rcu_read_lock(); - css = blkcg_css(); - if (!css_tryget_online(css)) - css = NULL; - rcu_read_unlock(); + if (bio_blkcg(bio)) + return; - bio_associate_blkg_from_css(bio, css); - if (css) - css_put(css); - } + rcu_read_lock(); + css = blkcg_css(); + if (!css_tryget_online(css)) + css = NULL; + rcu_read_unlock(); + + bio_associate_blkcg_from_css(bio, css); + if (css) + css_put(css); } -EXPORT_SYMBOL_GPL(bio_associate_blkg); +EXPORT_SYMBOL_GPL(bio_associate_blkcg); /** - * bio_clone_blkg_association - clone blkg association from src to dst bio + * bio_clone_blkcg_association - clone blkcg association from src to dst bio * @dst: destination bio * @src: source bio / -void bio_clone_blkg_association(struct bio dst, struct bio src) +void bio_clone_blkcg_association(struct bio dst, struct bio src) { - if (src->bi_blkg) - bio_associate_blkg_from_css(dst, bio_blkcg_css(src)); + if (bio_blkcg(src)) + bio_associate_blkcg_from_css(dst, bio_blkcg_css(src)); } -EXPORT_SYMBOL_GPL(bio_clone_blkg_association); +EXPORT_SYMBOL_GPL(bio_clone_blkcg_association); static int blk_cgroup_io_type(struct bio bio) { @@ -2181,20 +2231,27 @@ static int blk_cgroup_io_type(struct bio bio) void blk_cgroup_bio_start(struct bio bio) { - struct blkcg blkcg = bio->bi_blkg->blkcg; + struct blkcg blkcg = bio_blkcg(bio); + struct blkcg_gq blkg; int rwd = blk_cgroup_io_type(bio), cpu; struct blkg_iostat_set bis; unsigned long flags; if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) return; + if (!blkcg) + return; /* Root-level stats are sourced from system-wide IO stats / if (!cgroup_parent(blkcg->css.cgroup)) return; + blkg = bio_blkg_lookup(bio); + if (!blkg) + return; + cpu = get_cpu(); - bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu); + bis = per_cpu_ptr(blkg->iostat_cpu, cpu); flags = u64_stats_update_begin_irqsave(&bis->sync); / diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 615390f751aa2..b457c2b4ac7c8 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -73,14 +73,7 @@ struct blkcg_gq { struct blkg_iostat_set iostat; struct blkg_policy_data pd[BLKCG_MAX_POLS]; -#ifdef CONFIG_BLK_CGROUP_PUNT_BIO - spinlock_t async_bio_lock; - struct bio_list async_bios; -#endif - union { - struct work_struct async_bio_work; - struct work_struct free_work; - }; + struct work_struct free_work; atomic_t use_delay; atomic64_t delay_nsec; @@ -111,6 +104,11 @@ struct blkcg { / struct llist_head __percpu lhead; +#ifdef CONFIG_BLK_CGROUP_PUNT_BIO + spinlock_t async_bio_lock; + struct bio_list async_bios; + struct work_struct async_bio_work; +#endif #ifdef CONFIG_BLK_CGROUP_FC_APPID char fc_app_id[FC_APPID_LEN]; #endif @@ -124,6 +122,11 @@ static inline struct blkcg css_to_blkcg(struct cgroup_subsys_state css) return css ? container_of(css, struct blkcg, css) : NULL; } +static inline struct blkcg bio_blkcg(struct bio bio) +{ + return bio->bi_blkcg; +} + / * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a * request_queue (q). This is used by blkcg policies which need to track @@ -276,6 +279,9 @@ static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg, return blkg; } +struct blkcg_gq bio_blkg_lookup(struct bio bio); +struct blkcg_gq bio_blkg(struct bio bio); + /** * blkg_to_pd - get policy private data * @blkg: blkg of interest @@ -343,6 +349,18 @@ static inline void blkg_put(struct blkcg_gq blkg) percpu_ref_put(&blkg->refcnt); } +static inline void bio_clear_blkcg(struct bio bio) +{ + struct blkcg blkcg = bio_blkcg(bio); + + bio_put_blkg_ref(bio); + + if (blkcg) { + css_put(&blkcg->css); + bio->bi_blkcg = NULL; + } +} + /* * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants * @d_blkg: loop cursor pointing to the current descendant @@ -455,7 +473,7 @@ static inline void blkcg_clear_delay(struct blkcg_gq blkg) / static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio) { - return rq->bio->bi_blkg == bio->bi_blkg && + return bio_blkcg(rq->bio) == bio_blkcg(bio) && bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio); } @@ -481,6 +499,9 @@ struct blkcg_policy { struct blkcg { }; +static inline struct blkcg bio_blkcg(struct bio bio) { return NULL; } +static inline struct blkcg_gq bio_blkg_lookup(struct bio bio) { return NULL; } +static inline struct blkcg_gq bio_blkg(struct bio bio) { return NULL; } static inline struct blkcg_gq blkg_lookup(struct blkcg blkcg, void key) { return NULL; } static inline void blkg_init_queue(struct request_queue q) { } static inline int blkcg_init_disk(struct gendisk disk) { return 0; } @@ -497,6 +518,7 @@ static inline struct blkg_policy_data blkg_to_pd(struct blkcg_gq blkg, static inline struct blkcg_gq pd_to_blkg(struct blkg_policy_data pd) { return NULL; } static inline void blkg_get(struct blkcg_gq blkg) { } static inline void blkg_put(struct blkcg_gq blkg) { } +static inline void bio_clear_blkcg(struct bio bio) { } static inline void blk_cgroup_bio_start(struct bio bio) { } static inline bool blk_cgroup_mergeable(struct request rq, struct bio bio) { return true; } diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c index 2a5c52ab74b4c..5ef4baab444bb 100644 --- a/block/blk-crypto-fallback.c +++ b/block/blk-crypto-fallback.c @@ -187,7 +187,7 @@ static struct bio blk_crypto_alloc_enc_bio(struct bio bio_src, bio->bi_write_hint = bio_src->bi_write_hint; bio->bi_write_stream = bio_src->bi_write_stream; bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector; - bio_clone_blkg_association(bio, bio_src); + bio_clone_blkcg_association(bio, bio_src); / * Move page array up in the allocated memory for the bio vecs as far as diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 8b2aeba2e1e39..62ffd759bb954 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -2686,7 +2686,7 @@ iocg_handle_over_budget(struct rq_qos rqos, struct ioc_gq iocg, static void ioc_rqos_throttle(struct rq_qos rqos, struct bio bio) { - struct blkcg_gq blkg = bio->bi_blkg; + struct blkcg_gq blkg = bio_blkg(bio); struct ioc ioc = rqos_to_ioc(rqos); struct ioc_gq iocg = blkg_to_iocg(blkg); struct ioc_now now; @@ -2775,7 +2775,7 @@ static void ioc_rqos_throttle(struct rq_qos rqos, struct bio bio) static void ioc_rqos_merge(struct rq_qos rqos, struct request rq, struct bio bio) { - struct ioc_gq iocg = blkg_to_iocg(bio->bi_blkg); + struct ioc_gq iocg = blkg_to_iocg(bio_blkg_lookup(bio)); struct ioc ioc = rqos_to_ioc(rqos); sector_t bio_end = bio_end_sector(bio); struct ioc_now now; @@ -2833,9 +2833,13 @@ static void ioc_rqos_merge(struct rq_qos rqos, struct request rq, static void ioc_rqos_done_bio(struct rq_qos rqos, struct bio bio) { - struct ioc_gq iocg = blkg_to_iocg(bio->bi_blkg); + struct ioc_gq iocg; + + if (!bio->bi_iocost_cost) + return; - if (iocg && bio->bi_iocost_cost) + iocg = blkg_to_iocg(bio_blkg_lookup(bio)); + if (iocg) atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime); } diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index cef02b6c5fa91..7ad18a538d7e2 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -463,7 +463,7 @@ static void check_scale_change(struct iolatency_grp iolat) static void blkcg_iolatency_throttle(struct rq_qos rqos, struct bio bio) { struct blk_iolatency blkiolat = BLKIOLATENCY(rqos); - struct blkcg_gq blkg = bio->bi_blkg; + struct blkcg_gq blkg = bio_blkg(bio); bool issue_as_root = bio_issue_as_root_blkg(bio); if (!blkiolat->enabled) @@ -590,11 +590,14 @@ static void blkcg_iolatency_done_bio(struct rq_qos rqos, struct bio bio) bool issue_as_root = bio_issue_as_root_blkg(bio); int inflight = 0; - blkg = bio->bi_blkg; - if (!blkg \|\| !bio_flagged(bio, BIO_QOS_THROTTLED)) + if (!bio_flagged(bio, BIO_QOS_THROTTLED)) return; - iolat = blkg_to_lat(bio->bi_blkg); + blkg = bio_blkg_lookup(bio); + if (!blkg) + return; + + iolat = blkg_to_lat(blkg); if (!iolat) return; diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c index 8fa8bca350629..5e3f8e49550da 100644 --- a/block/blk-ioprio.c +++ b/block/blk-ioprio.c @@ -132,7 +132,7 @@ static struct blkcg_policy ioprio_policy = { void blkcg_set_ioprio(struct bio bio) { - struct ioprio_blkcg blkcg = blkcg_to_ioprio_blkcg(bio->bi_blkg->blkcg); + struct ioprio_blkcg blkcg = blkcg_to_ioprio_blkcg(bio_blkcg(bio)); u16 prio; if (!blkcg \|\| blkcg->prio_policy == POLICY_NO_CHANGE) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index ffc3b70065d4b..3828c38579002 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -1792,7 +1792,7 @@ static bool tg_within_limit(struct throtl_grp tg, struct bio bio, bool rw) bool __blk_throtl_bio(struct bio bio) { struct request_queue q = bdev_get_queue(bio->bi_bdev); - struct blkcg_gq blkg = bio->bi_blkg; + struct blkcg_gq blkg = bio_blkg(bio); struct throtl_qnode qn = NULL; struct throtl_grp tg = blkg_to_tg(blkg); struct throtl_service_queue sq; diff --git a/block/blk-throttle.h b/block/blk-throttle.h index 9d7a42c039a15..609a126c7ccb2 100644 --- a/block/blk-throttle.h +++ b/block/blk-throttle.h @@ -173,7 +173,7 @@ static inline bool blk_should_throtl(struct bio bio) if (!blk_throtl_activated(bio->bi_bdev->bd_queue)) return false; - tg = blkg_to_tg(bio->bi_blkg); + tg = blkg_to_tg(bio_blkg(bio)); if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) { if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { bio_set_flag(bio, BIO_CGROUP_ACCT); diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index 3fa3b13a410f4..c0f945b8d9413 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -848,7 +848,7 @@ static CLOSURE_CALLBACK(cached_dev_read_done) s->iop.bio->bi_iter.bi_sector = s->cache_miss->bi_iter.bi_sector; s->iop.bio->bi_iter.bi_size = s->insert_bio_sectors << 9; - bio_clone_blkg_association(s->iop.bio, s->cache_miss); + bio_clone_blkcg_association(s->iop.bio, s->cache_miss); bch_bio_map(s->iop.bio, NULL); bio_copy_data(s->cache_miss, s->iop.bio); diff --git a/drivers/md/dm.c b/drivers/md/dm.c index d413bfaf35278..cd68eec77f5a1 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1373,7 +1373,7 @@ void dm_submit_bio_remap(struct bio clone, struct bio tgt_clone) if (!tgt_clone) tgt_clone = clone; - bio_clone_blkg_association(tgt_clone, io->orig_bio); + bio_clone_blkcg_association(tgt_clone, io->orig_bio); / * Account io->origin_bio to DM dev on behalf of target diff --git a/drivers/md/md.c b/drivers/md/md.c index d1465bcd86c81..af55f8efa46bc 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9355,7 +9355,7 @@ void md_submit_discard_bio(struct mddev mddev, struct md_rdev rdev, return; bio_chain(discard_bio, bio); - bio_clone_blkg_association(discard_bio, bio); + bio_clone_blkcg_association(discard_bio, bio); mddev_trace_remap(mddev, discard_bio, bio->bi_iter.bi_sector); submit_bio_noacct(discard_bio); } diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c index 4176046627beb..54e4adb0ccb7d 100644 --- a/drivers/nvdimm/nd_virtio.c +++ b/drivers/nvdimm/nd_virtio.c @@ -121,7 +121,7 @@ int async_pmem_flush(struct nd_region nd_region, struct bio bio) if (!child) return -ENOMEM; - bio_clone_blkg_association(child, bio); + bio_clone_blkcg_association(child, bio); child->bi_iter.bi_sector = -1; bio_chain(child, bio); submit_bio(child); diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c index 6dabe73ad790d..6512dbd9516fc 100644 --- a/fs/gfs2/lops.c +++ b/fs/gfs2/lops.c @@ -484,7 +484,7 @@ static struct bio gfs2_chain_bio(struct bio prev, unsigned int nr_iovecs, struct bio new; new = bio_alloc(prev->bi_bdev, nr_iovecs, opf, GFP_NOIO); - bio_clone_blkg_association(new, prev); + bio_clone_blkcg_association(new, prev); new->bi_iter.bi_sector = sector; bio_chain(new, prev); submit_bio(prev); @@ -1114,4 +1114,3 @@ const struct gfs2_log_operations gfs2_log_ops[] = { &gfs2_revoke_lops, NULL, }; - diff --git a/include/linux/bio.h b/include/linux/bio.h index 8f33f717b14f5..e5799fdf431d2 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -503,18 +503,20 @@ static inline void bio_release_pages(struct bio bio, bool mark_dirty) disk_devt((bio)->bi_bdev->bd_disk) #ifdef CONFIG_BLK_CGROUP -void bio_associate_blkg(struct bio bio); -void bio_associate_blkg_from_css(struct bio bio, +void bio_associate_blkcg(struct bio bio); +void bio_associate_blkcg_from_css(struct bio bio, struct cgroup_subsys_state css); -void bio_clone_blkg_association(struct bio dst, struct bio src); +void bio_clone_blkcg_association(struct bio dst, struct bio src); +void bio_put_blkg_ref(struct bio bio); void blkcg_punt_bio_submit(struct bio bio); #else /* CONFIG_BLK_CGROUP / -static inline void bio_associate_blkg(struct bio bio) { } -static inline void bio_associate_blkg_from_css(struct bio bio, +static inline void bio_associate_blkcg(struct bio bio) { } +static inline void bio_associate_blkcg_from_css(struct bio bio, struct cgroup_subsys_state css) { } -static inline void bio_clone_blkg_association(struct bio dst, +static inline void bio_clone_blkcg_association(struct bio dst, struct bio src) { } +static inline void bio_put_blkg_ref(struct bio bio) { } static inline void blkcg_punt_bio_submit(struct bio bio) { submit_bio(bio); @@ -524,10 +526,12 @@ static inline void blkcg_punt_bio_submit(struct bio bio) static inline void bio_set_dev(struct bio bio, struct block_device bdev) { bio_clear_flag(bio, BIO_REMAPPED); - if (bio->bi_bdev != bdev) + if (bio->bi_bdev != bdev) { + bio_put_blkg_ref(bio); bio_clear_flag(bio, BIO_BPS_THROTTLED); + } bio->bi_bdev = bdev; - bio_associate_blkg(bio); + bio_associate_blkcg(bio); } /* diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 8808ee76e73c0..5f95c2e0e90b0 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -246,12 +246,10 @@ struct bio { void bi_private; #ifdef CONFIG_BLK_CGROUP / - * Represents the association of the css and request_queue for the bio. - * If a bio goes direct to device, it will not have a blkg as it will - * not have a request_queue associated with it. The reference is put - * on release of the bio. + * Represents the blkcg css association for the bio. The reference is + * put on release of the bio. / - struct blkcg_gq bi_blkg; + struct blkcg bi_blkcg; / Time that this bio was issued. / u64 issue_time_ns; #ifdef CONFIG_BLK_CGROUP_IOCOST @@ -309,6 +307,7 @@ enum { BIO_TRACE_COMPLETION, / bio_endio() should trace the final completion * of this bio. / BIO_CGROUP_ACCT, / has been accounted to a cgroup / + BIO_BLKG_REF, / bio pins the associated blkg / BIO_QOS_THROTTLED, / bio went through rq_qos throttle path / / * This bio has completed bps throttling at the single tg granularity, diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 62552a2ce5b9e..4f869fe9cc90f 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -262,7 +262,7 @@ static inline void wbc_init_bio(struct writeback_control wbc, struct bio bio) * regular writeback instead of writing things out itself. / if (wbc->wb) - bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css); + bio_associate_blkcg_from_css(bio, wbc->wb->blkcg_css); } void inode_switch_wbs_work_fn(struct work_struct work); diff --git a/mm/page_io.c b/mm/page_io.c index b23f494fcc83d..112e504756055 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -316,7 +316,7 @@ static inline void count_swpout_vm_event(struct folio folio) } #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) -static void bio_associate_blkg_from_page(struct bio bio, struct folio folio) +static void bio_associate_blkcg_from_page(struct bio bio, struct folio folio) { struct cgroup_subsys_state css; struct mem_cgroup memcg; @@ -331,12 +331,12 @@ static void bio_associate_blkg_from_page(struct bio bio, struct folio folio) css = NULL; rcu_read_unlock(); - bio_associate_blkg_from_css(bio, css); + bio_associate_blkcg_from_css(bio, css); if (css) css_put(css); } #else -#define bio_associate_blkg_from_page(bio, folio) do { } while (0) +#define bio_associate_blkcg_from_page(bio, folio) do { } while (0) #endif / CONFIG_MEMCG && CONFIG_BLK_CGROUP / struct swap_iocb { @@ -436,7 +436,7 @@ static void swap_writepage_bdev_sync(struct folio folio, bio.bi_iter.bi_sector = swap_folio_sector(folio); bio_add_folio_nofail(&bio, folio, folio_size(folio), 0); - bio_associate_blkg_from_page(&bio, folio); + bio_associate_blkcg_from_page(&bio, folio); count_swpout_vm_event(folio); folio_start_writeback(folio); @@ -456,7 +456,7 @@ static void swap_writepage_bdev_async(struct folio *folio, bio->bi_end_io = end_swap_bio_write; bio_add_folio_nofail(bio, folio, folio_size(folio), 0); - bio_associate_blkg_from_page(bio, folio); + bio_associate_blkcg_from_page(bio, folio); count_swpout_vm_event(folio); folio_start_writeback(folio); folio_unlock(folio);
3/2	2026/08/04 07:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 16348 output: 21 thoughts: 478 Thoughts: Analyzing a Core Block Layer Change for Block Cgroup Association Okay, so I'm looking at a patch that fundamentally alters how `bio` structures relate to `blkcg` (block cgroups). They're replacing `bio->bi_blkg` with `bio->bi_blkcg`, and introducing new functions, `bio_blkg_lookup()` and `bio_blkg()`. This is a pretty significant change, really digging into the core of how block I/O interacts with cgroups. The sheer number of files touched is a dead giveaway: `block/bfq-cgroup.c`, `block/bfq-iosched.c`, `block/bio.c`, `block/blk-cgroup-fc-appid.c`, `block/blk-cgroup.c`, and so on, all the way through to `mm/page_io.c`, plus header files like `include/linux/bio.h`. It really touches a broad swath of the block layer. This isn't just a cosmetic tweak; it's a deep dive into the functional logic of how we look up and pin the `blkg` structure associated with a `bio`. That's critical, especially for things like I/O scheduling and throttling. This is going to impact virtualized environments, too. I'll need to pay close attention to the implications there. Now, let's figure out what configuration options are needed for this. I'm guessing `CONFIG_BLK_CGROUP` is a given; it's right in the name of the change. `CONFIG_BFQ_GROUP_IOSCHED` is mentioned in the BFQ scheduler, so that's probably related. Then there's `CONFIG_BLK_CGROUP_PUNT_BIO`, `CONFIG_BLK_CGROUP_IOCOST`, and `CONFIG_BLK_CGROUP_IOLATENCY`. I should probably use `grepper` to be sure I haven't missed anything, and make sure I know the exact config names.
4/2	2026/08/04 07:16	tool	grepper	0m Args: { "Expression": "config BLK_CGROUP" } Results: { "Output": "block/Kconfig=39=config BLK_RQ_ALLOC_TIME\n--\nblock/Kconfig-41-\nblock/Kconfig:42:config BLK_CGROUP_RWSTAT\nblock/Kconfig-43-\tbool\nblock/Kconfig-44-\nblock/Kconfig:45:config BLK_CGROUP_PUNT_BIO\nblock/Kconfig-46-\tbool\n--\nblock/Kconfig=127=config BLK_WBT_MQ\n--\nblock/Kconfig-133-\nblock/Kconfig:134:config BLK_CGROUP_IOLATENCY\nblock/Kconfig-135-\tbool \"Enable support for latency based cgroup IO protection\"\n--\nblock/Kconfig-144-\nblock/Kconfig:145:config BLK_CGROUP_FC_APPID\nblock/Kconfig-146-\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n--\nblock/Kconfig-153-\nblock/Kconfig:154:config BLK_CGROUP_IOCOST\nblock/Kconfig-155-\tbool \"Enable support for cost model based cgroup IO controller\"\n--\nblock/Kconfig-163-\nblock/Kconfig:164:config BLK_CGROUP_IOPRIO\nblock/Kconfig-165-\tbool \"Cgroup I/O controller for assigning an I/O priority class\"\n--\ninit/Kconfig=1099=config MEMCG_V1\n--\ninit/Kconfig-1115-\ninit/Kconfig:1116:config BLK_CGROUP\ninit/Kconfig-1117-\tbool \"IO controller\"\n" }
5/2	2026/08/04 07:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 17720 output: 23 thoughts: 12 Thoughts: Okay, here's my attempt at summarizing that thought process, tailored for an expert audience: BFQ Configuration Name Hunt Alright, time to get laser-focused. I need to pinpoint the exact configuration names associated with BFQ. No ambiguity here – I'm looking for the precise identifiers, the variables, the options, whatever the system uses to internally define and manage BFQ's behavior. I can't afford to be vague or use generic terminology; I need the nitty-gritty details. Are we talking kernel parameters? Module options? Configuration files? I'm going to dig until I find the definitive source that clearly lays out the naming conventions. It's time to sift through documentation, source code, and perhaps even some debugging output to make absolutely sure I have the accurate config names.
6/2	2026/08/04 07:16	tool	grepper	0m Args: { "Expression": "config BFQ_GROUP_IOSCHED" } Results: { "Output": "block/Kconfig.iosched=19=config IOSCHED_BFQ\n--\nblock/Kconfig.iosched-29-\nblock/Kconfig.iosched:30:config BFQ_GROUP_IOSCHED\nblock/Kconfig.iosched-31- bool \"BFQ hierarchical scheduling support\"\n" }
7/2	2026/08/04 07:16	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 18016 output: 25 thoughts: 266 Thoughts: Analyzing Block I/O Cgroup Functionality Alright, let's dive into this block I/O cgroup implementation. First, I need to keep the relevant configuration options in mind: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, and `BFQ_GROUP_IOSCHED`. These are the flags defining what's enabled. Now, let's list out the core functions that manage the cgroup association and lifecycle of block I/O operations. I'm focusing on these: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, and `bio_clear_blkcg`. These should be the heart of the interaction. Okay, next I quickly check which of these functions are actually exposed. And the answer is "All of them!". Excellent. That means this is a relatively self-contained, well-defined set of building blocks. Good to know. Time to head into `block/blk-cgroup.c` and dig into the implementation details of each. This is where the real work happens. Let's see how these pieces fit together.
8/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL_GPL\\(bio_blkg" } Results: { "Output": "block/blk-cgroup.c=2074=struct blkcg_gq bio_blkg_lookup(struct bio bio)\n--\nblock/blk-cgroup.c-2096-}\nblock/blk-cgroup.c:2097:EXPORT_SYMBOL_GPL(bio_blkg_lookup);\nblock/blk-cgroup.c-2098-\n--\nblock/blk-cgroup.c=2125=struct blkcg_gq bio_blkg(struct bio bio)\n--\nblock/blk-cgroup.c-2150-}\nblock/blk-cgroup.c:2151:EXPORT_SYMBOL_GPL(bio_blkg);\nblock/blk-cgroup.c-2152-\n" }
9/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 18825 output: 27 thoughts: 23 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing `bio_associate_blkcg` and `bio_clone_blkcg_association` Alright, time to dig into `bio_associate_blkcg` and `bio_clone_blkcg_association`. These are key for block device CGroups, so let's make sure our understanding is rock solid. I need to be completely clear on the responsibilities of each of these functions. From what I recall, `bio_associate_blkcg` is the primary entry point for, well, associating a bio (Block IO request) with a specific blkcg (Block CGroup). I need to re-examine the mechanics of how it handles the association: Is it a direct assignment, or does it involve some sort of internal tracking or metadata update? I need to clarify the interaction between the bio's context and the target blkcg. `bio_clone_blkcg_association`... now, that one's interesting. The name suggests this handles cloning the blkcg association when a bio is duplicated or split, perhaps. Is it a deep copy or shallow copy? I want to pay attention to how they handle the propagation of the blkcg association through bio cloning. It seems critical for preserving resource accounting across complex bio operations, which may require special consideration when it comes to nested or shared CGroups. I should also make sure to check the locking around these functions, especially if they are called in interrupt context or from multiple threads. Concurrency issues around blkcg association could lead to performance problems or, worse, data corruption. Let's make sure the details of synchronization are sound.
10/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL_GPL\\(bio_associate_blkcg" } Results: { "Output": "block/blk-cgroup.c=2164=void bio_associate_blkcg_from_css(struct bio bio,\n--\nblock/blk-cgroup.c-2179-}\nblock/blk-cgroup.c:2180:EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css);\nblock/blk-cgroup.c-2181-\n--\nblock/blk-cgroup.c=2189=void bio_associate_blkcg(struct bio bio)\n--\nblock/blk-cgroup.c-2208-}\nblock/blk-cgroup.c:2209:EXPORT_SYMBOL_GPL(bio_associate_blkcg);\nblock/blk-cgroup.c-2210-\n" }
11/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 19430 output: 29 thoughts: 11 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm an expert in this field, presented as a first-person summary: The Crucial `bio_clone_blkcg_association` Consideration Alright, so the core of my thinking here centers around this function, `bio_clone_blkcg_association`. I immediately understand the implication – we're dealing with cloning, likely a `bio` structure, and it's intimately tied to block I/O and control groups (blkcg). My brain instantly starts running through the scenarios: what's the context? Is this about a copy-on-write operation, a remapping, or something else entirely? The fact that we're talking about cloning suggests that we need to be careful about resource attribution and tracking. Specifically, how do we correctly propagate the blkcg association across the cloned `bio`? Are we creating a completely new association or maintaining the existing one? If it's the latter, we have to consider the potential pitfalls of shared resources and race conditions. If it is the former, what is the right way to determine that information? Are there implications for the I/O scheduler and accounting? My expertise kicks in here, reminding me to consider potential memory management issues and synchronization needs. We need to be wary of making the blkcg association part of the `bio` itself. That could be problematic. I need to dive into the specific code and the surrounding context. It is important to know if the `blkcg` association is going to be used by the scheduler. And if so, should the scheduler treat this as a new I/O with different weights? What is the impact of accounting? This function is right at the heart of how we manage resources and isolation within the block I/O stack and I know it's a critical point for performance and correctness. Any errors here could lead to cascading problems down the line. I must scrutinize this carefully.
12/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL_GPL\\(bio_clone_blkcg_association" } Results: { "Output": "block/blk-cgroup.c=2216=void bio_clone_blkcg_association(struct bio dst, struct bio src)\n--\nblock/blk-cgroup.c-2220-}\nblock/blk-cgroup.c:2221:EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);\nblock/blk-cgroup.c-2222-\n" }
13/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 19988 output: 29 thoughts: 11 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Working with `bio_put_blkg_ref` Right, so I see we're dealing with `bio_put_blkg_ref`. Immediately, my mind jumps to the implications for block device interactions within the BIOS environment. This suggests a low-level, critical function, likely involved in managing block references, and potentially handling the intricacies of memory allocation and deallocation specifically within the context of the BIOS. I'm imagining it's the core of how we manipulate persistent storage at the most fundamental level. We're probably talking about handling different types of block device types, such as disk drives, solid-state drives, or perhaps even virtual block devices. Given the naming convention, I’m guessing this isn’t a simple wrapper. It feels like a key piece to managing data structures related to block references. I need to understand the underlying data structures it operates on. What data types are involved? Are we dealing with lists, trees, or perhaps something more specialized for managing block maps or extents? The interaction with the underlying hardware, and how these references are translated into physical disk addresses, will be critical. Furthermore, I have to consider the potential for race conditions. If it’s not thread-safe, or if locking isn't handled correctly, we could easily corrupt data. I need to know how it interfaces with any other concurrent operations or interrupt handlers within the BIOS. Error handling is paramount, too. How robust is the error handling? What kind of checks are in place to prevent data loss or system instability if something goes wrong? Are there any retry mechanisms? This likely plays a crucial role in our boot process stability. Finally, I’m thinking about performance. Is this function optimized for speed? Are there any potential bottlenecks, especially with large block sizes or frequent write operations? And how does it relate to the `bio_` framework? It's likely a critical component of block I/O operations and I need to consider it's implications in that context.
14/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL_GPL\\(bio_put_blkg_ref" } Results: { "Output": "block/blk-cgroup.c=2105=void bio_put_blkg_ref(struct bio *bio)\n--\nblock/blk-cgroup.c-2113-}\nblock/blk-cgroup.c:2114:EXPORT_SYMBOL_GPL(bio_put_blkg_ref);\nblock/blk-cgroup.c-2115-\n" }
15/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 20573 output: 29 thoughts: 128 Thoughts: Adding New Block IO CGroups Functions Okay, so I've been working on these new Block IO CGroups functions, and I need to make sure they're properly documented and integrated. I'm going to add them to the `FocusSymbols` list so they're easily tracked and considered for future work. That means including: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and then making sure the updated `blkcg_punt_bio_submit` function is included too. Wait a second, `blkcg_punt_bio_submit` was already present. I need to double-check that this function is properly exported. I need to make sure there are no issues with it being changed. I will check for this.
16/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "EXPORT_SYMBOL_GPL\\(blkcg_punt_bio_submit" } Results: { "Output": "block/blk-cgroup.c=235=void blkcg_punt_bio_submit(struct bio *bio)\n--\nblock/blk-cgroup.c-248-}\nblock/blk-cgroup.c:249:EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);\nblock/blk-cgroup.c-250-\n" }
17/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 21031 output: 26 thoughts: 664 Thoughts: Analyzing Block Layer CGROUP API Changes Okay, so I'm looking at these changes and the first thing that jumps out is that it is an API change. My first thought is to dig into the implementation, and I need to be careful about not documenting static inline functions, like `bio_clear_blkcg` which is defined in `block/blk-cgroup.h`, or static functions, like `bio_pinned_blkg`, found in `block/blk-cgroup.c`. I have to remember this when I am documenting them. I need to make sure I don't miss anything, so let me do a quick scan of other functions involved. Let's see... there's `bfq_bio_bfqg`, `bfq_bio_merge`, `bfq_insert_request`, some `bio` manipulation functions in `block/bio.c` (`bio_uninit`, `bio_init`, `bio_reset`, `__bio_clone`, `bio_endio`), and a few others that I need to keep in mind, like the ones in the cgroup specific files like `blkcg_get_fc_appid`, `blk_cgroup_bio_start`, `blk_crypto_alloc_enc_bio`, `ioc_rqos_throttle`, `ioc_rqos_merge`, `ioc_rqos_done_bio`, `blkcg_iolatency_throttle`, `blkcg_iolatency_done_bio`, `blkcg_set_ioprio`, and `__blk_throtl_bio`. The key change here, though, seems to be a new set of API functions. Let's focus on these new additions: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, and `bio_put_blkg_ref`. Those seem to be the critical ones that make the core API change. I'll need to go back and investigate the configuration options that are affected by this. I need to make sure to document that: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `BLK_CGROUP_FC_APPID`, and `BLK_CGROUP_PUNT_BIO` are all affected. Right now, I should focus on `bio_blkg_lookup` and `bio_blkg`, as those seem to be the critical changes in this new API. I will need to verify the usage of `BLK_CGROUP_PUNT_BIO` and how that affects the block layer as well, so I'll need to go and look into that in Kconfig.
18/2	2026/08/04 07:17	tool	grepper	0m Args: { "Expression": "config BLK_CGROUP_PUNT_BIO" } Results: { "Output": "block/Kconfig=42=config BLK_CGROUP_RWSTAT\n--\nblock/Kconfig-44-\nblock/Kconfig:45:config BLK_CGROUP_PUNT_BIO\nblock/Kconfig-46-\tbool\n" }
19/2	2026/08/04 07:17	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 22428 output: 26 thoughts: 33 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, and delivered as a first-person summary: Digging into a Mysterious Boolean Right, so this flag, this boolean, it's not exposed directly. It's hidden. That immediately tells me it's being toggled by something else within the system. We can't simply flip the switch ourselves, we have to understand the why and the how of its activation. So, my next step is clear: I need to trace back through the code, or examine the configuration, whatever relevant mechanisms are present, to figure out what's actually selecting this hidden bool. What conditions are triggering it? What dependencies are at play? I need to get to the root cause to understand its purpose and how to interact with it effectively. That's the only way to work with this properly.
20/2	2026/08/04 07:18	tool	grepper	0m Args: { "Expression": "select BLK_CGROUP_PUNT_BIO" } Results: { "Output": "fs/btrfs/Kconfig=3=config BTRFS_FS\nfs/btrfs/Kconfig-4-\ttristate \"Btrfs filesystem support\"\nfs/btrfs/Kconfig:5:\tselect BLK_CGROUP_PUNT_BIO\nfs/btrfs/Kconfig-6-\tselect CRC32\n" }
21/2	2026/08/04 07:18	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 22771 output: 26 thoughts: 42 Thoughts: Okay, here's my interpretation of those thoughts, considering my expertise: Checking the BTRFS and Block CGroups Alright, it looks like the configuration process has landed on `BTRFS_FS`. Excellent. So the system logic is selecting this, and it makes sense. I can go ahead and incorporate `BTRFS_FS` directly into the configurations. That's a straightforward step. Now, let's turn our attention to `BLK_CGROUP_FC_APPID`. I need to ensure that the proper controls are in place and that those are properly configured as well. This will impact the overall performance and resource allocation, so it's critical to verify its setup.
22/2	2026/08/04 07:18	tool	grepper	0m Args: { "Expression": "config BLK_CGROUP_FC_APPID" } Results: { "Output": "block/Kconfig=134=config BLK_CGROUP_IOLATENCY\n--\nblock/Kconfig-144-\nblock/Kconfig:145:config BLK_CGROUP_FC_APPID\nblock/Kconfig-146-\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n" }
23/2	2026/08/04 07:18	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 23083 output: 32 thoughts: 29 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person: Navigating the Storage Protocol Labyrinth Alright, so the immediate question at hand hinges on the underlying storage protocol in play here. My initial thought process is to determine if we're dealing with `NVME_FC` or `SCSI_FC_ATTRS`. This is the critical juncture for this line of inquiry. Given this dependency, my next step is a deep dive into the `block/Kconfig` configuration file. That's where I need to confirm the conditions for the inclusion of the functionality. Understanding the Kconfig dependencies will immediately clarify the configuration path and relevant configurations. From there, I can determine the appropriate steps for the required modifications.
24/2	2026/08/04 07:18	tool	read-file	0m Args: { "File": "block/Kconfig", "FirstLine": 140, "LineCount": 20 } Results: { "Contents": " 140:\t\tthe configured latency target, throttling anybody with a higher latency\n 141:\t\ttarget than the victimized group.\n 142:\t\n 143:\t\tNote, this is an experimental interface and could be changed someday.\n 144:\t\n 145:\tconfig BLK_CGROUP_FC_APPID\n 146:\t\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n 147:\t\tdepends on BLK_CGROUP \u0026\u0026 NVME_FC\n 148:\t\thelp\n 149:\t\t Enabling this option enables the support to track FC I/O traffic across\n 150:\t\t cgroup applications. It enables the Fabric and the storage targets to\n 151:\t\t identify, monitor, and handle FC traffic based on VM tags by inserting\n 152:\t\t application specific identification into the FC frame.\n 153:\t\n 154:\tconfig BLK_CGROUP_IOCOST\n 155:\t\tbool \"Enable support for cost model based cgroup IO controller\"\n 156:\t\tdepends on BLK_CGROUP\n 157:\t\tselect BLK_RQ_ALLOC_TIME\n 158:\t\thelp\n 159:\t\tEnabling this option enables the .weight interface for cost\n" }
25/2	2026/08/04 07:18	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 23638 output: 32 thoughts: 38 Thoughts: Okay, here's my interpretation of those thoughts, presented as my own mental process, with the assumption I'm an expert in this field. Navigating Storage and Control Groups Alright, so it's clear that we're dealing with a specific interaction here. It seems the `NVME_FC` functionality is a prerequisite for correctly handling `BLK_CGROUP_FC_APPID`. That makes sense; the NVMe-FC protocol likely sets up the foundational framework for flow control and application ID management at a higher level, potentially interacting with the cgroup configuration. I need to make sure I understand the dependencies clearly. Now, let's pivot to a related area. Since we're in this space, I need to take a look at how `BLK_CGROUP_IOPRIO` interacts with the configuration as well. It could be that the flow control settings and the I/O priority settings should be integrated in a certain way. This check is crucial for optimizing overall performance and preventing conflicts. Gotta make sure everything is cohesive within the cgroup and storage setup. Let's see how these interact.
26/2	2026/08/04 07:18	tool	read-file	0m Args: { "File": "block/Kconfig", "FirstLine": 160, "LineCount": 20 } Results: { "Contents": " 160:\t\tmodel based proportional IO control. The IO controller\n 161:\t\tdistributes IO capacity between different groups based on\n 162:\t\ttheir share of the overall weight distribution.\n 163:\t\n 164:\tconfig BLK_CGROUP_IOPRIO\n 165:\t\tbool \"Cgroup I/O controller for assigning an I/O priority class\"\n 166:\t\tdepends on BLK_CGROUP\n 167:\t\thelp\n 168:\t\tEnable the .prio interface for assigning an I/O priority class to\n 169:\t\trequests. The I/O priority class affects the order in which an I/O\n 170:\t\tscheduler and block devices process requests. Only some I/O schedulers\n 171:\t\tand some block devices support I/O priorities.\n 172:\t\n 173:\tconfig BLK_DEBUG_FS\n 174:\t\tbool \"Block layer debugging information in debugfs\"\n 175:\t\tdefault y\n 176:\t\tdepends on DEBUG_FS\n 177:\t\thelp\n 178:\t\tInclude block layer debugging information in debugfs. This information\n 179:\t\tis mostly useful for kernel developers, but it doesn't incur any cost\n" }
27/2	2026/08/04 07:18	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 24269 output: 19 thoughts: 115 Thoughts: Analyzing Block Device Configuration Options Alright, let's take a look at these block device configurations. I see we've got a list here: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, then `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, and some NVMe and Btrfs options with `NVME_FC`, `BLK_CGROUP_FC_APPID`, and `BTRFS_FS`. My initial thought is to quickly ascertain any potential dependencies, to better understand how these pieces fit together. For starters, let me check into `NVME_FC` specifically. That's a good place to begin my analysis.
28/2	2026/08/04 07:18	tool	grepper	0m Args: { "Expression": "config NVME_FC" } Results: { "Output": "drivers/nvme/host/Kconfig=52=config NVME_RDMA\n--\ndrivers/nvme/host/Kconfig-66-\ndrivers/nvme/host/Kconfig:67:config NVME_FC\ndrivers/nvme/host/Kconfig-68-\ttristate \"NVM Express over Fabrics FC host driver\"\n" }
29/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 24672 output: 36 thoughts: 15 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Diving into the NVMe Host Kconfig Alright, let's crack open `drivers/nvme/host/Kconfig`. This is where the core configuration options for the NVMe host controller driver reside, and understanding this file is key to customizing and optimizing its behavior. I need to refresh my memory on the specific configuration knobs available. First, I'll be looking for any architectural assumptions or dependencies it defines, particularly relating to the platform's interrupt handling. Are there any processor-specific sections I need to keep in mind, or is this largely platform-agnostic? Next, I'll scan for options related to features like multi-queue support, AER (Advanced Error Reporting), and potentially even specific NVMe version support if there's any branching in the code. I'll need to pay close attention to the default values and help text for each option. These defaults often expose the project's priorities and the typical target hardware. I'll be checking if there are any specific options tied to specific vendor controllers, to know what hardware is fully supported and what requires a bit of customization. I'll be particularly interested in the option dependencies and their implications. Are there options that imply a certain hardware configuration? What are the implications of enabling or disabling them, especially in terms of performance and power consumption? Finally, I'll need to keep an eye out for any "tricky" bits – conditional compilation based on other kernel configurations, potential conflicts, or anything that could subtly affect the driver's integration with the rest of the storage stack. The goal here is to get a handle on the available configuration space and how to effectively leverage it for a given deployment scenario.
30/2	2026/08/04 07:19	tool	read-file	0m Args: { "File": "drivers/nvme/host/Kconfig", "FirstLine": 60, "LineCount": 20 } Results: { "Contents": " 60:\t\t to use remote block devices exported using the NVMe protocol set.\n 61:\t\n 62:\t\t To configure a NVMe over Fabrics controller use the nvme-cli tool\n 63:\t\t from https://github.com/linux-nvme/nvme-cli.\n 64:\t\n 65:\t\t If unsure, say N.\n 66:\t\n 67:\tconfig NVME_FC\n 68:\t\ttristate \"NVM Express over Fabrics FC host driver\"\n 69:\t\tdepends on BLOCK\n 70:\t\tdepends on HAS_DMA\n 71:\t\tselect NVME_FABRICS\n 72:\t\tselect SG_POOL\n 73:\t\thelp\n 74:\t\t This provides support for the NVMe over Fabrics protocol using\n 75:\t\t the FC transport. This allows you to use remote block devices\n 76:\t\t exported using the NVMe protocol set.\n 77:\t\n 78:\t\t To configure a NVMe over Fabrics controller use the nvme-cli tool\n 79:\t\t from https://github.com/linux-nvme/nvme-cli.\n" }
31/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25385 output: 20 thoughts: 23 Thoughts: Here's my take on those thoughts: Evaluating Storage Options Alright, so `NVME_FC` seems like a solid choice for now. That meets the fundamental performance requirements. But, I need to take a wider look at the system to ensure I haven't missed any edge cases and performance bottlenecks. I should also evaluate `BTRFS_FS`, especially given its flexibility and data management features. I need to make sure I'm not overlooking a better solution for this particular scenario, considering the long-term implications and potential for future expansion or optimization.
32/2	2026/08/04 07:19	tool	grepper	0m Args: { "Expression": "config BTRFS_FS" } Results: { "Output": "fs/btrfs/Kconfig-2-\nfs/btrfs/Kconfig:3:config BTRFS_FS\nfs/btrfs/Kconfig-4-\ttristate \"Btrfs filesystem support\"\n--\nfs/btrfs/Kconfig-38-\nfs/btrfs/Kconfig:39:config BTRFS_FS_POSIX_ACL\nfs/btrfs/Kconfig-40-\tbool \"Btrfs POSIX Access Control Lists\"\n--\nfs/btrfs/Kconfig-48-\nfs/btrfs/Kconfig:49:config BTRFS_FS_RUN_SANITY_TESTS\nfs/btrfs/Kconfig-50-\tbool \"Btrfs will run sanity tests upon loading\"\n" }
33/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25744 output: 21 thoughts: 23 Thoughts: Here's my take on those thoughts: Evaluating the Storage Setup Okay, so `BTRFS_FS` is confirmed. No immediate red flags there. Now, the next logical step is to delve into the I/O scheduler. Let's see how `IOSCHED_BFQ` is performing within this specific configuration. I need to understand its impact on overall system performance and how it interacts with `BTRFS`. There could be subtle interactions I need to identify.
34/2	2026/08/04 07:19	tool	grepper	0m Args: { "Expression": "config IOSCHED_BFQ" } Results: { "Output": "block/Kconfig.iosched=10=config MQ_IOSCHED_KYBER\n--\nblock/Kconfig.iosched-18-\nblock/Kconfig.iosched:19:config IOSCHED_BFQ\nblock/Kconfig.iosched-20-\ttristate \"BFQ I/O scheduler\"\n" }
35/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 25981 output: 23 thoughts: 26 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: Kernel I/O Scheduler Assessment Alright, so `IOSCHED_BFQ` – that's looking good, as expected. Seems like the base BFQ implementation is holding its own. However, I need to dig a little deeper. The true test is often how these schedulers handle the more complex group structures. So, I'm going to shift my focus. Let's get into investigating `BFQ_GROUP_IOSCHED`. The grouping aspect is where things get really interesting, and where we'll likely uncover any hidden performance bottlenecks or scalability issues related to how BFQ deals with I/O isolation between different application groups. That's the key now.
36/2	2026/08/04 07:19	tool	grepper	0m Args: { "Expression": "config BFQ_GROUP_IOSCHED" } Results: { "Output": "block/Kconfig.iosched=19=config IOSCHED_BFQ\n--\nblock/Kconfig.iosched-29-\nblock/Kconfig.iosched:30:config BFQ_GROUP_IOSCHED\nblock/Kconfig.iosched-31- bool \"BFQ hierarchical scheduling support\"\n" }
37/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 26284 output: 34 thoughts: 28 Thoughts: Okay, here's my summary, expressed as though I'm thinking it: Thinking Through BFQ's Dependencies Alright, let's break this down. BFQ_GROUP_IOSCHED... right, that's the thing that lets us do I/O scheduling per cgroup. Makes sense. But it's not a standalone feature, is it? It relies heavily on IOSCHED_BFQ, the actual BFQ scheduler itself. We can't have per-cgroup BFQ without the base BFQ functionality. And further, if we're doing cgroup-based scheduling, then BLK_CGROUP is absolutely foundational. It's the infrastructure that provides the whole cgroup hierarchy and resource management framework for block devices in the first place. So, without BLK_CGROUP, IOSCHED_BFQ wouldn't work, and neither would BFQ_GROUP_IOSCHED. It's a clear dependency chain: cgroups, then the scheduler, then the group scheduler implementation. Got it.
38/2	2026/08/04 07:19	tool	read-file	0m Args: { "File": "block/Kconfig.iosched", "FirstLine": 25, "LineCount": 20 } Results: { "Contents": " 25:\t\tregardless of the device parameters and with any workload. It\n 26:\t\talso guarantees a low latency to interactive and soft\n 27:\t\treal-time applications. Details in\n 28:\t\tDocumentation/block/bfq-iosched.rst\n 29:\t\n 30:\tconfig BFQ_GROUP_IOSCHED\n 31:\t bool \"BFQ hierarchical scheduling support\"\n 32:\t depends on IOSCHED_BFQ \u0026\u0026 BLK_CGROUP\n 33:\t default y\n 34:\t select BLK_CGROUP_RWSTAT\n 35:\t\thelp\n 36:\t\n 37:\t Enable hierarchical scheduling in BFQ, using the blkio\n 38:\t (cgroups-v1) or io (cgroups-v2) controller.\n 39:\t\n 40:\tconfig BFQ_CGROUP_DEBUG\n 41:\t\tbool \"BFQ IO controller debugging\"\n 42:\t\tdepends on BFQ_GROUP_IOSCHED\n 43:\t\thelp\n 44:\t\tEnable some debugging help. Currently it exports additional stat\n" }
39/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 26864 output: 32 thoughts: 308 Thoughts: Analyzing Block I/O Cgroup Configuration Options Alright, I've got a solid list of block I/O cgroup configuration options to consider. We have `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, and `BTRFS_FS`. This looks like a good starting point for understanding how different features interact. Now, from what I recall, `bio_blkg_lookup` and `bio_blkg` are the core functions here. I need to make sure I haven't missed any other crucial functions though. Let me quickly scan for related functions... Okay, I see `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`. This seems like a reasonable set of supporting functions. Good, now to see if `bio_put_blkg_ref` is exported. Yes, it looks like it is, which is important for external modules to interact with it. I should probably double-check the configs one more time, to make sure there are no other dependencies I need to be aware of. Okay, `CONFIG_BLK_CGROUP_PUNT_BIO` is selected by `BTRFS_FS`, that's a key interaction to remember. I also see that `CONFIG_BLK_CGROUP_FC_APPID` depends on either `NVME_FC` or `SCSI_FC_ATTRS`. Wait, let me just confirm the exact dependencies for `BLK_CGROUP_FC_APPID` so I can fully understand this.
40/2	2026/08/04 07:19	tool	read-file	0m Args: { "File": "block/Kconfig", "FirstLine": 140, "LineCount": 10 } Results: { "Contents": " 140:\t\tthe configured latency target, throttling anybody with a higher latency\n 141:\t\ttarget than the victimized group.\n 142:\t\n 143:\t\tNote, this is an experimental interface and could be changed someday.\n 144:\t\n 145:\tconfig BLK_CGROUP_FC_APPID\n 146:\t\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n 147:\t\tdepends on BLK_CGROUP \u0026\u0026 NVME_FC\n 148:\t\thelp\n 149:\t\t Enabling this option enables the support to track FC I/O traffic across\n" }
41/2	2026/08/04 07:19	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 27796 output: 17 thoughts: 59 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, as if they were my own mental process: Configuration Dependency Deep Dive Right, this is about the `BLK_CGROUP` and `NVME_FC` configs. It's clear that the code flow relies on `NVME_FC` being enabled; that's a given. I need to figure out what other dependencies might exist. Specifically, the mention of `CONFIG_MEMCG` in `mm/page_io.c` has caught my eye. It's often the case that seemingly unrelated subsystems share dependencies, especially when you're dealing with block I/O and memory management. It's likely that if `MEMCG` is enabled there are implications for how `NVME_FC` interacts with it. That could open an interesting rabbit hole that needs to be explored. Let's see what the interactions are.
42/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "config MEMCG" } Results: { "Output": "init/Kconfig=1066=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1075-\ninit/Kconfig:1076:config MEMCG\ninit/Kconfig-1077-\tbool \"Memory controller\"\n--\ninit/Kconfig-1084-\ninit/Kconfig:1085:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1086-\tbool\n--\ninit/Kconfig-1091-\ninit/Kconfig:1092:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1093-\tbool\n--\ninit/Kconfig-1098-\ninit/Kconfig:1099:config MEMCG_V1\ninit/Kconfig-1100-\tbool \"Legacy cgroup v1 memory controller\"\n" }
43/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 28296 output: 28 thoughts: 520 Thoughts: Analyzing Hot-Path Functions for Focused Fuzzing Okay, so I'm thinking about how to construct the `FocusSymbols` list for fuzzing this code. `MEMCG` is definitely a good starting point. Let's look at the functions that relate to block cgroups. First, I see: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`. I have to consider the prompt's instruction to avoid generic hot-path functions to prevent test distributions from being skewed. I know `bio_blkg_lookup` and `bio_blkg` are called frequently on the I/O path. `bio_associate_blkcg` is in `bio_init`, `bio_reset` and `bio_set_dev`. `bio_clone_blkcg_association` is in `__bio_clone`. `bio_put_blkg_ref` is in `bio_clear_blkcg`, which is called in `bio_uninit` and `bio_endio`. These are very hot-path. But, the prompt specifically tells me to prioritize non-static, non-inlined API entrypoints functions, so these would be good. However, `bio_blkg` and `bio_blkg_lookup` are specific to block cgroups and are new or modified by this patch. While hot-path for block I/O, they are the very functions I want to focus on. So, I think I'll include them. The prompt says to avoid generic hot-path functions, but `bio_blkg` and `bio_blkg_lookup` are the main new functions and are exactly what I need to focus the fuzzing on. `blkcg_punt_bio_submit` is another one. It's called when bouncing bios for cgroups, which makes it less hot-path. I think that is still okay to include. `bfq_bio_bfqg` is specific to BFQ, which is another interesting candidate, and I'll include `blkcg_get_fc_appid` as well, as that's FC appid specific. So, I'm going to include: `bio_blkg`, `bio_blkg_lookup`, `blkcg_punt_bio_submit`, `blkcg_get_fc_appid`, and `bfq_bio_bfqg`. Now, let's just make sure that `bfq_bio_bfqg` is exported and non-static...
44/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "struct bfq_group \\bfq_bio_bfqg" } Results:* { "Output": "block/bfq-cgroup.c=586=static void bfq_link_bfqg(struct bfq_data bfqd, struct bfq_group bfqg)\n--\nblock/bfq-cgroup.c-608-\nblock/bfq-cgroup.c:609:struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio)\nblock/bfq-cgroup.c-610-{\n--\nblock/bfq-cgroup.c=1439=void bfq_end_wr_async(struct bfq_data bfqd)\n--\nblock/bfq-cgroup.c-1445-\nblock/bfq-cgroup.c:1446:struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio)\nblock/bfq-cgroup.c-1447-{\n--\nblock/bfq-iosched.h=1086=void bfq_end_wr_async(struct bfq_data bfqd);\nblock/bfq-iosched.h:1087:struct bfq_group bfq_bio_bfqg(struct bfq_data bfqd, struct bio bio);\nblock/bfq-iosched.h-1088-struct blkcg_gq bfqg_to_blkg(struct bfq_group *bfqg);\n" }
45/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 29806 output: 24 thoughts: 21 Thoughts: Okay, here's my summary, tailored as requested: Assessing Dynamic State Right, this situation isn't static. We need to understand the moving parts. My initial instinct is to go deeper into a specific function. Let's see... the most relevant function in this context would be `blkcg_get_fc_appid`. Time to dig in and see what's happening there. That's the key to understanding the non-static element.
46/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "char \\blkcg_get_fc_appid" } Results:* { "Output": "block/blk-cgroup-fc-appid.c=43=EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);\n--\nblock/blk-cgroup-fc-appid.c-50- /\nblock/blk-cgroup-fc-appid.c:51:char blkcg_get_fc_appid(struct bio bio)\nblock/blk-cgroup-fc-appid.c-52-{\n--\ninclude/linux/blk-cgroup.h=48=int blkcg_set_fc_appid(char app_id, u64 cgrp_id, size_t app_id_len);\ninclude/linux/blk-cgroup.h:49:char blkcg_get_fc_appid(struct bio bio);\ninclude/linux/blk-cgroup.h-50-\n" }
47/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 30162 output: 23 thoughts: 18 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing the Exported Function Right, so it's been flagged as "exported." That immediately triggers a mental checklist: what's the context? What is exported? Is it a kernel symbol, a userspace interface, a module export, or something else entirely? The implications are vastly different depending on the specific situation. The level of abstraction here is key - what is being exported, and where is it going? My immediate follow-up thought is to dive into the particulars of `blkcg_set_ioprio`. This function name itself already tells a story. "blkcg" suggests block I/O control groups. So, this probably deals with setting I/O priorities within a control group context. Now I need to consider, from an expert's point of view: Are we talking about the original cgroup v1 implementation, or the newer cgroup v2? What about the specific data structures involved? Is it related to the `ioprio` class, and its associated parameters? Or is it a part of scheduling or bandwidth enforcement, etc? And how does this connect to my current line of thinking and my project goals. I need to refresh the knowledge of the implementation so that I am familiar with the latest changes and improvements. I have a long list of things to consider. I hope it is all up-to-date.
48/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "void blkcg_set_ioprio" } Results: { "Output": "block/blk-ioprio.c=125=static struct blkcg_policy ioprio_policy = {\n--\nblock/blk-ioprio.c-132-\nblock/blk-ioprio.c:133:void blkcg_set_ioprio(struct bio bio)\nblock/blk-ioprio.c-134-{\n--\nblock/blk-ioprio.h=9=struct bio;\n--\nblock/blk-ioprio.h-11-#ifdef CONFIG_BLK_CGROUP_IOPRIO\nblock/blk-ioprio.h:12:void blkcg_set_ioprio(struct bio bio);\nblock/blk-ioprio.h-13-#else\nblock/blk-ioprio.h:14:static inline void blkcg_set_ioprio(struct bio *bio)\nblock/blk-ioprio.h-15-{\n" }
49/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 30730 output: 24 thoughts: 34 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person: Analyzing Dynamic IO Behavior Right, this isn't a static situation. I need to dig deeper. Something's clearly fluctuating, and I'm guessing it has to do with how IO latency is managed. Let's see... my initial instinct is to drill down into the control group IO latency mechanisms. I'll need to examine the interactions of `blkcg_iolatency_throttle` and `blkcg_iolatency_done_bio` particularly. These are the key functions responsible for throttling IO based on latency targets and signaling completion. I need to understand the sequencing and the potential bottlenecks within those. Perhaps there's a runaway condition, a miscalculation somewhere, or even contention for resources. Let's pull up the code and dive in. I need to understand what's actually happening at that level to pinpoint the root cause.
50/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "void blkcg_iolatency_throttle" } Results: { "Output": "block/blk-iolatency.c=399=static void check_scale_change(struct iolatency_grp iolat)\n--\nblock/blk-iolatency.c-462-\nblock/blk-iolatency.c:463:static void blkcg_iolatency_throttle(struct rq_qos rqos, struct bio *bio)\nblock/blk-iolatency.c-464-{\n" }
51/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 31109 output: 22 thoughts: 35 Thoughts: Okay, here's my interpretation of those thoughts, crafted with the understanding that I'm discussing this with a fellow expert: Internal Review of IO QoS Handling Alright, the current picture seems...fixed. Stagnant. I need to make sure I'm not missing something fundamental. This feels like the kind of situation where a subtle oversight could cause big problems later on, so let's start with a systematic review. Let's see if there are any obvious issues. My immediate focus then shifts to those specific functions: `ioc_rqos_throttle`, `ioc_rqos_merge`, and `ioc_rqos_done_bio`. I need to re-examine how these functions are handling the I/O QoS aspects. Are the throttling mechanisms behaving as expected under various workloads? What about the merging logic? And, of course, how are we signaling completion? There could be a subtle race condition in any of these. I need to verify how these interact. I need to fully understand if there are any holes in the logic in any of these, given the state of the system that I see currently.
52/2	2026/08/04 07:20	tool	grepper	0m Args: { "Expression": "void ioc_rqos_throttle" } Results: { "Output": "block/blk-iocost.c=2613=iocg_handle_over_budget(struct rq_qos rqos, struct ioc_gq iocg,\n--\nblock/blk-iocost.c-2686-\nblock/blk-iocost.c:2687:static void ioc_rqos_throttle(struct rq_qos rqos, struct bio bio)\nblock/blk-iocost.c-2688-{\n" }
53/2	2026/08/04 07:20	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 31525 output: 22 thoughts: 18 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Assessing a Potential Bottleneck Hmm, things feel…stuck. Static. That's never good, especially when performance is on the line. I need to pinpoint the constraint. Let's dig into the details. My gut tells me this could be a throttling issue. I immediately think of the block layer. Specifically, I should check `__blk_throtl_bio`. That's where I'd expect to find the queueing logic and any potential bottlenecks related to I/O scheduling and prioritization. It's a key function for understanding how I/O requests are handled, and checking its state will give me a very solid starting point to diagnose any performance issues.
54/2	2026/08/04 07:21	tool	grepper	0m Args: { "Expression": "bool __blk_throtl_bio" } Results: { "Output": "block/blk-throttle.c=1764=static bool tg_within_limit(struct throtl_grp tg, struct bio bio, bool rw)\n--\nblock/blk-throttle.c-1791-\nblock/blk-throttle.c:1792:bool __blk_throtl_bio(struct bio bio)\nblock/blk-throttle.c-1793-{\n--\nblock/blk-throttle.h=153=void blk_throtl_exit(struct gendisk disk);\nblock/blk-throttle.h:154:bool __blk_throtl_bio(struct bio bio);\nblock/blk-throttle.h-155-void blk_throtl_cancel_bios(struct gendisk disk);\n" }
55/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 31924 output: 26 thoughts: 348 Thoughts: Analyzing Block IO and Control Group Interactions Okay, so I'm looking at this code and it's definitely dynamic, not static. I need to figure out the key functions related to block IO and control group (blkcg) association. Let's see... I'll check what's exported and relevant. Right, `bio_blkg_lookup` and `bio_blkg` are both exported, which is a good starting point. Then we have `bio_associate_blkcg_from_css` and `bio_associate_blkcg` which are also exported - interesting. Plus, there's `bio_clone_blkcg_association` and `bio_put_blkg_ref` that are exported. Based on that, I'd say the "FocusSymbols" should include: * `bio_blkg_lookup` * `bio_blkg` * `bio_associate_blkcg_from_css` * `bio_associate_blkcg` * `bio_clone_blkcg_association` * `bio_put_blkg_ref` * `blkcg_punt_bio_submit` * `bfq_bio_bfqg` * `blkcg_get_fc_appid` * `blkcg_set_ioprio` * `__blk_throtl_bio` Wait a minute, `bio_associate_blkcg_from_css` seems like it could be a crucial, hot-path function, but it's being specifically modified here. I think focusing in on the following functions would make the most sense for the current task: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`. Let me quickly look at `bio_associate_blkcg_from_page` though. Okay, so it's a static function, defined within `mm/page_io.c`. Not directly relevant here, but good to know. And let's also check out `bfqg_stats_update_legacy_io`.
56/2	2026/08/04 07:21	tool	grepper	0m Args: { "Expression": "void bfqg_stats_update_legacy_io" } Results: { "Output": "block/bfq-cgroup.c=357=void bfqg_and_blkg_put(struct bfq_group bfqg)\n--\nblock/bfq-cgroup.c-363-\nblock/bfq-cgroup.c:364:void bfqg_stats_update_legacy_io(struct request_queue q, struct request rq)\nblock/bfq-cgroup.c-365-{\n--\nblock/bfq-iosched.h=1060=void bfq_put_async_queues(struct bfq_data bfqd, struct bfq_group bfqg);\n--\nblock/bfq-iosched.h-1065-\nblock/bfq-iosched.h:1066:void bfqg_stats_update_legacy_io(struct request_queue q, struct request rq);\nblock/bfq-iosched.h-1067-void bfqg_stats_update_io_remove(struct bfq_group bfqg, blk_opf_t opf);\n" }
57/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 33065 output: 24 thoughts: 21 Thoughts: Okay, here's my attempt at summarizing those thoughts from a first-person, expert perspective, aiming for a fulsome rendering: Analyzing the Dynamic Nature Right, this situation is not static. That's the first thing that jumps out at me. We're dealing with a dynamic process, and understanding its evolution is key. I need to dig deeper into the root cause. This isn't a one-off event. The next step is clear: I need to investigate what's happening internally, and the best place to start is often at the beginning. Let's start by looking at `blk_cgroup_bio_start`. I have a feeling that function will provide some crucial insights into the initial conditions, control mechanisms, or potential for unexpected behavior in this evolving system. From there, I can trace its impact through the relevant code paths. It's the logical starting point for understanding this dynamic process.
58/2	2026/08/04 07:21	tool	grepper	0m Args: { "Expression": "void blk_cgroup_bio_start" } Results: { "Output": "block/blk-cgroup.c=2223=static int blk_cgroup_io_type(struct bio bio)\n--\nblock/blk-cgroup.c-2231-\nblock/blk-cgroup.c:2232:void blk_cgroup_bio_start(struct bio bio)\nblock/blk-cgroup.c-2233-{\n--\nblock/blk-cgroup.h=480=static inline bool blkcg_policy_enabled(struct request_queue q,\n--\nblock/blk-cgroup.h-485-\nblock/blk-cgroup.h:486:void blk_cgroup_bio_start(struct bio bio);\nblock/blk-cgroup.h-487-void blkcg_add_delay(struct blkcg_gq blkg, u64 now, u64 delta);\n--\nblock/blk-cgroup.h=521=static inline void bio_clear_blkcg(struct bio bio) { }\nblock/blk-cgroup.h:522:static inline void blk_cgroup_bio_start(struct bio bio) { }\nblock/blk-cgroup.h-523-static inline bool blk_cgroup_mergeable(struct request rq, struct bio *bio) { return true; }\n" }
59/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 33643 output: 21 thoughts: 342 Thoughts: Refining the Block I/O Cgroup Focus Okay, this needs to be dynamic, not static. I need to make sure I'm capturing everything correctly for the Block I/O Cgroup analysis. First, I need to refine that `FocusSymbols` list. Let's see... I'll start with this group: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, `bfq_bio_bfqg`, `blkcg_get_fc_appid`, `blkcg_set_ioprio`, `__blk_throtl_bio`, `bfqg_stats_update_legacy_io`, `blk_cgroup_bio_start`. Wait a minute, `bio_associate_blkcg_from_css` really is a key function here. I'll need to keep that one in mind. Now, I should make sure I haven't missed any related configuration options. Looking at that `bio_associate_blkcg_from_page` function in `mm/page_io.c`, it looks like `CONFIG_MEMCG` is required for that particular function. I'll need to add `MEMCG` to my configuration list. So, here's my updated configuration list to consider: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, `BTRFS_FS` and finally, that important `MEMCG` setting. Now I need to check how `CONFIG_CGROUP_WRITEBACK` might fit in.
60/2	2026/08/04 07:21	tool	grepper	0m Args: { "Expression": "config CGROUP_WRITEBACK" } Results: { "Output": "init/Kconfig=1116=config BLK_CGROUP\n--\ninit/Kconfig-1137-\ninit/Kconfig:1138:config CGROUP_WRITEBACK\ninit/Kconfig-1139-\tbool\n" }
61/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 34515 output: 21 thoughts: 15 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Analyzing a Boolean Flag Okay, so I've stumbled upon a hidden boolean variable. My initial instinct is to dig deeper and understand its purpose and behavior. My primary focus right now is to identify all the points in the code that are reading or writing to this flag. I need to trace back from where it's defined and figure out what logic paths are controlling its state. Is it being set based on a specific input, a calculation, a condition, a user action, a data event? Or maybe a combination of these elements? Once I understand the selectors, then I can ascertain its purpose.
62/2	2026/08/04 07:21	tool	grepper	0m Error: no matches Args: { "Expression": "select CGROUP_WRITEBACK" } Results: { "error": "no matches" }
63/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 34708 output: 33 thoughts: 21 Thoughts: Here's my thought process, as if I were considering this myself: Kconfig Dive for CGROUP_WRITEBACK Okay, before I go any further down this rabbit hole, I need to verify something fundamental. I should probably double check the `init/Kconfig` file in the kernel source. Specifically, I need to confirm whether or not `CGROUP_WRITEBACK` is defined. This option is critical for [insert your field's relevance to cgroup writeback here - e.g., enabling background data flushing in my storage subsystem work], and I need to make sure I understand its current state before moving on to consider its usage or implications further. Without this verification, I could waste time investigating something that may not even be present or enabled in the current configuration. Gotta check the Kconfig.
64/2	2026/08/04 07:21	tool	read-file	0m Args: { "File": "init/Kconfig", "FirstLine": 1130, "LineCount": 20 } Results: { "Contents": "1130:\t\tThis option only enables generic Block IO controller infrastructure.\n1131:\t\tOne needs to also enable actual IO controlling logic/policy. For\n1132:\t\tenabling proportional weight division of disk bandwidth in CFQ, set\n1133:\t\tCONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set\n1134:\t\tCONFIG_BLK_DEV_THROTTLING=y.\n1135:\t\n1136:\t\tSee Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.\n1137:\t\n1138:\tconfig CGROUP_WRITEBACK\n1139:\t\tbool\n1140:\t\tdepends on MEMCG \u0026\u0026 BLK_CGROUP\n1141:\t\tdefault y\n1142:\t\n1143:\tmenuconfig CGROUP_SCHED\n1144:\t\tbool \"CPU controller\"\n1145:\t\tdefault n\n1146:\t\thelp\n1147:\t\t This feature lets CPU scheduler recognize task groups and control CPU\n1148:\t\t bandwidth allocation to such task groups. It uses cgroups to group\n1149:\t\t tasks.\n" }
65/2	2026/08/04 07:21	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 35243 output: 24 thoughts: 57 Thoughts: My Configuration Musings Okay, so I see this default behavior when both `MEMCG` and `BLK_CGROUP` are enabled, defaulting to 'y'. That simplifies things a bit; it means if those two are set, we're likely good. My focus is narrowed. Now, let's just confirm. I need to take a look at `CONFIG_BLK_DEV_THROTTLING`. That's where the real magic happens, so I'll see what the configuration there tells us.
66/2	2026/08/04 07:21	tool	grepper	0m Args: { "Expression": "config BLK_DEV_THROTTLING" } Results: { "Output": "block/Kconfig=97=config BLK_DEV_ZONED\n--\nblock/Kconfig-105-\nblock/Kconfig:106:config BLK_DEV_THROTTLING\nblock/Kconfig-107-\tbool \"Block layer bio throttling support\"\n" }
67/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 35517 output: 26 thoughts: 47 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Adding Block Device Throttling Support Right, so I see we need this for `__blk_throtl_bio`. Makes perfect sense. Seems like the logical next step is to add `BLK_DEV_THROTTLING`. That'll give us the foundation we need. Now, let me just quickly double-check... I need to make sure we consider the implications of `CONFIG_BLK_DEV_THROTTLING_LOW`, because depending on how that's defined, it will affect how this functions. Gotta make sure we cover all our bases.
68/2	2026/08/04 07:22	tool	grepper	0m Error: no matches Args: { "Expression": "config BLK_DEV_THROTTLING_LOW" } Results: { "error": "no matches" }
69/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 35746 output: 16 thoughts: 25 Thoughts: Okay, here's my take on those seemingly simple thoughts: Dissecting the Kernel Configuration Landscape Right, so, the focus is clearly on kernel configuration, specifically related to storage or block device management. The phrase `BLK_DEV_THROTTLING` immediately triggers a mental scan. My initial assessment is that this is the core concern, likely indicating a need to manage I/O performance on block devices, potentially to prevent resource starvation or maintain quality of service. It's a fundamental aspect of system stability and responsiveness, so it makes sense to nail this down first. Now, the follow-up, `CONFIG_MD`. Ah, this is telling. The jump to `CONFIG_MD` (likely meaning Multiple Devices or RAID support) suggests that the throttling might be in the context of a RAID array or some form of logical volume management. We need to consider how the block device throttling interacts with the complexities introduced by data striping, mirroring, and parity calculations. Are we optimizing for a particular RAID level? Is there a performance bottleneck related to how the kernel interacts with the underlying physical devices in the array? This calls for careful examination. This is all about balancing the needs of different components.
70/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config MD" } Results: { "Output": "drivers/clk/qcom/Kconfig=563=config MSM_LCC_8960\n--\ndrivers/clk/qcom/Kconfig-571-\ndrivers/clk/qcom/Kconfig:572:config MDM_GCC_9607\ndrivers/clk/qcom/Kconfig-573-\ttristate \"MDM9607 Global Clock Controller\"\n--\ndrivers/clk/qcom/Kconfig-579-\ndrivers/clk/qcom/Kconfig:580:config MDM_GCC_9615\ndrivers/clk/qcom/Kconfig-581-\ttristate \"MDM9615 Global Clock Controller\"\n--\ndrivers/md/Kconfig-5-\ndrivers/md/Kconfig:6:menuconfig MD\ndrivers/md/Kconfig-7-\tbool \"Multiple devices driver support (RAID and LVM)\"\n--\ndrivers/md/Kconfig=15=config BLK_DEV_MD\n--\ndrivers/md/Kconfig-39-\ndrivers/md/Kconfig:40:config MD_BITMAP\ndrivers/md/Kconfig-41-\tbool \"MD RAID bitmap support\"\n--\ndrivers/md/Kconfig-54-\ndrivers/md/Kconfig:55:config MD_LLBITMAP\ndrivers/md/Kconfig-56-\tbool \"MD RAID lockless bitmap support\"\n--\ndrivers/md/Kconfig-65-\ndrivers/md/Kconfig:66:config MD_AUTODETECT\ndrivers/md/Kconfig-67-\tbool \"Autodetect RAID arrays during kernel boot\"\n--\ndrivers/md/Kconfig-79-\ndrivers/md/Kconfig:80:config MD_BITMAP_FILE\ndrivers/md/Kconfig-81-\tbool \"MD bitmap file support (deprecated)\"\n--\ndrivers/md/Kconfig-90-\ndrivers/md/Kconfig:91:config MD_LINEAR\ndrivers/md/Kconfig-92-\ttristate \"Linear (append) mode\"\n--\ndrivers/md/Kconfig-103-\ndrivers/md/Kconfig:104:config MD_RAID0\ndrivers/md/Kconfig-105-\ttristate \"RAID-0 (striping) mode\"\n--\ndrivers/md/Kconfig-123-\ndrivers/md/Kconfig:124:config MD_RAID1\ndrivers/md/Kconfig-125-\ttristate \"RAID-1 (mirroring) mode\"\n--\ndrivers/md/Kconfig-145-\ndrivers/md/Kconfig:146:config MD_RAID10\ndrivers/md/Kconfig-147-\ttristate \"RAID-10 (mirrored striping) mode\"\n--\ndrivers/md/Kconfig-164-\ndrivers/md/Kconfig:165:config MD_RAID456\ndrivers/md/Kconfig-166-\ttristate \"RAID-4/RAID-5/RAID-6 mode\"\n--\ndrivers/md/Kconfig-201-\ndrivers/md/Kconfig:202:config MD_CLUSTER\ndrivers/md/Kconfig-203-\ttristate \"Cluster Support for MD\"\n--\ndrivers/net/ethernet/Kconfig=13=if ETHERNET\ndrivers/net/ethernet/Kconfig-14-\ndrivers/net/ethernet/Kconfig:15:config MDIO\ndrivers/net/ethernet/Kconfig-16-\ttristate\n--\ndrivers/net/mdio/Kconfig=19=config ACPI_MDIO\n--\ndrivers/net/mdio/Kconfig-23-\ndrivers/net/mdio/Kconfig:24:config MDIO_AIROHA\ndrivers/net/mdio/Kconfig-25-\ttristate \"Airoha AN7583 MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-30-\ndrivers/net/mdio/Kconfig:31:config MDIO_SUN4I\ndrivers/net/mdio/Kconfig-32-\ttristate \"Allwinner sun4i MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-38-\ndrivers/net/mdio/Kconfig:39:config MDIO_XGENE\ndrivers/net/mdio/Kconfig-40-\ttristate \"APM X-Gene SoC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-45-\ndrivers/net/mdio/Kconfig:46:config MDIO_ASPEED\ndrivers/net/mdio/Kconfig-47-\ttristate \"ASPEED MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-58-\ndrivers/net/mdio/Kconfig:59:config MDIO_BITBANG\ndrivers/net/mdio/Kconfig-60-\ttristate \"Bitbanged MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-67-\ndrivers/net/mdio/Kconfig:68:config MDIO_BCM_IPROC\ndrivers/net/mdio/Kconfig-69-\ttristate \"Broadcom iProc MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-76-\ndrivers/net/mdio/Kconfig:77:config MDIO_BCM_UNIMAC\ndrivers/net/mdio/Kconfig-78-\ttristate \"Broadcom UniMAC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-85-\ndrivers/net/mdio/Kconfig:86:config MDIO_CAVIUM\ndrivers/net/mdio/Kconfig-87-\ttristate\ndrivers/net/mdio/Kconfig-88-\ndrivers/net/mdio/Kconfig:89:config MDIO_GPIO\ndrivers/net/mdio/Kconfig-90-\ttristate \"GPIO lib-based bitbanged MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-98-\ndrivers/net/mdio/Kconfig:99:config MDIO_HISI_FEMAC\ndrivers/net/mdio/Kconfig-100-\ttristate \"Hisilicon FEMAC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-105-\ndrivers/net/mdio/Kconfig:106:config MDIO_I2C\ndrivers/net/mdio/Kconfig-107-\ttristate\n--\ndrivers/net/mdio/Kconfig-115-\ndrivers/net/mdio/Kconfig:116:config MDIO_MVUSB\ndrivers/net/mdio/Kconfig-117-\ttristate \"Marvell USB to MDIO Adapter\"\n--\ndrivers/net/mdio/Kconfig-122-\ndrivers/net/mdio/Kconfig:123:config MDIO_MSCC_MIIM\ndrivers/net/mdio/Kconfig-124-\ttristate \"Microsemi MIIM interface support\"\n--\ndrivers/net/mdio/Kconfig-131-\ndrivers/net/mdio/Kconfig:132:config MDIO_MOXART\ndrivers/net/mdio/Kconfig-133-\ttristate \"MOXA ART MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-138-\ndrivers/net/mdio/Kconfig:139:config MDIO_OCTEON\ndrivers/net/mdio/Kconfig-140-\ttristate \"Octeon and some ThunderX SOCs MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-148-\ndrivers/net/mdio/Kconfig:149:config MDIO_PIC64HPSC\ndrivers/net/mdio/Kconfig-150-\ttristate \"PIC64-HPSC/HX MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-156-\ndrivers/net/mdio/Kconfig:157:config MDIO_IPQ4019\ndrivers/net/mdio/Kconfig-158-\ttristate \"Qualcomm IPQ4019 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-164-\ndrivers/net/mdio/Kconfig:165:config MDIO_IPQ8064\ndrivers/net/mdio/Kconfig-166-\ttristate \"Qualcomm IPQ8064 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-172-\ndrivers/net/mdio/Kconfig:173:config MDIO_REALTEK_RTL9300\ndrivers/net/mdio/Kconfig-174-\ttristate \"Realtek RTL9300 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-179-\ndrivers/net/mdio/Kconfig:180:config MDIO_REGMAP\ndrivers/net/mdio/Kconfig-181-\ttristate\n--\ndrivers/net/mdio/Kconfig-190-\ndrivers/net/mdio/Kconfig:191:config MDIO_THUNDER\ndrivers/net/mdio/Kconfig-192-\ttristate \"ThunderX SOCs MDIO buses\"\n--\ndrivers/net/mdio/Kconfig=201=comment \"MDIO Multiplexers\"\ndrivers/net/mdio/Kconfig-202-\ndrivers/net/mdio/Kconfig:203:config MDIO_BUS_MUX\ndrivers/net/mdio/Kconfig-204-\ttristate\n--\ndrivers/net/mdio/Kconfig-211-\ndrivers/net/mdio/Kconfig:212:config MDIO_BUS_MUX_MESON_G12A\ndrivers/net/mdio/Kconfig-213-\ttristate \"Amlogic G12a based MDIO bus multiplexer\"\n--\ndrivers/net/mdio/Kconfig-222-\ndrivers/net/mdio/Kconfig:223:config MDIO_BUS_MUX_MESON_GXL\ndrivers/net/mdio/Kconfig-224-\ttristate \"Amlogic GXL based MDIO bus multiplexer\"\n--\ndrivers/net/mdio/Kconfig-233-\ndrivers/net/mdio/Kconfig:234:config MDIO_BUS_MUX_BCM6368\ndrivers/net/mdio/Kconfig-235-\ttristate \"Broadcom BCM6368 MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-244-\ndrivers/net/mdio/Kconfig:245:config MDIO_BUS_MUX_BCM_IPROC\ndrivers/net/mdio/Kconfig-246-\ttristate \"Broadcom iProc based MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-255-\ndrivers/net/mdio/Kconfig:256:config MDIO_BUS_MUX_GPIO\ndrivers/net/mdio/Kconfig-257-\ttristate \"GPIO controlled MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-265-\ndrivers/net/mdio/Kconfig:266:config MDIO_BUS_MUX_MULTIPLEXER\ndrivers/net/mdio/Kconfig-267-\ttristate \"MDIO bus multiplexer using kernel multiplexer subsystem\"\n--\ndrivers/net/mdio/Kconfig-277-\ndrivers/net/mdio/Kconfig:278:config MDIO_BUS_MUX_MMIOREG\ndrivers/net/mdio/Kconfig-279-\ttristate \"MMIO device-controlled MDIO bus multiplexers\"\n" }
71/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 38952 output: 17 thoughts: 28 Thoughts: Okay, here's my take on those thoughts, framed as my own: Adding Support for MD and Checking BCACHE Right, let's get down to brass tacks. I'm looking at configuring this system, and it's clear that the Multi-Device (MD) subsystem needs to be properly addressed. The first thing that jumps out is the need to enable the `BLK_DEV_MD` configuration option. That's a no-brainer; we need that kernel support if we're going to utilize MD arrays. Okay, noted, and I'll add that right away. Now, a related area that I need to quickly scan, and which I'm already thinking about is `BCACHE`. It's a technology related to caching, and it is a good idea to perform a quick check and see how it interacts with the current setup. I'll make sure it plays nicely, and isn't something that might introduce conflicts later. Let me make a note to investigate that interaction further.
72/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config BCACHE" } Results: { "Output": "drivers/md/bcache/Kconfig-2-\ndrivers/md/bcache/Kconfig:3:config BCACHE\ndrivers/md/bcache/Kconfig-4-\ttristate \"Block device as cache\"\n--\ndrivers/md/bcache/Kconfig-13-\ndrivers/md/bcache/Kconfig:14:config BCACHE_DEBUG\ndrivers/md/bcache/Kconfig-15-\tbool \"Bcache debugging\"\n--\ndrivers/md/bcache/Kconfig-22-\ndrivers/md/bcache/Kconfig:23:config BCACHE_ASYNC_REGISTRATION\ndrivers/md/bcache/Kconfig-24-\tbool \"Asynchronous device registration\"\n" }
73/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 39393 output: 21 thoughts: 20 Thoughts: Okay, here's my take on those initial thoughts, framed as a concise internal monologue: Considering Storage Optimization Alright, I'm thinking we should definitely incorporate `BCACHE`. It's a proven solution for accelerating storage performance, and it's something I've had good results with in the past. Now, before we get too far down that road, I need to double-check the interaction with `BLK_DEV_DM`. It's critical to ensure there are no compatibility conflicts or performance bottlenecks between these two layers. That's the priority at this moment. Let's make sure it is fully compatible before proceeding.
74/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config BLK_DEV_DM" } Results: { "Output": "drivers/md/Kconfig=219=source \"drivers/md/bcache/Kconfig\"\ndrivers/md/Kconfig-220-\ndrivers/md/Kconfig:221:config BLK_DEV_DM_BUILTIN\ndrivers/md/Kconfig-222-\tbool\ndrivers/md/Kconfig-223-\ndrivers/md/Kconfig:224:config BLK_DEV_DM\ndrivers/md/Kconfig-225-\ttristate \"Device mapper support\"\n" }
75/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 39707 output: 24 thoughts: 26 Thoughts: Here's my take on those thoughts: Considering Block Device Drivers and Encryption Okay, so I'm thinking about incorporating `BLK_DEV_DM` – Data Mapper block devices – into the system. It's a key piece for things like logical volumes, snapshots, and encryption at the block level. I'm wondering about the implications of integrating that. We need to be mindful of performance, complexity, and how it interacts with other drivers. Then, my mind wanders to `BLK_INLINE_ENCRYPTION`. That's another vital area, especially for security-conscious deployments. I'm assessing whether to enable it, I need to understand its capabilities. I should explore its advantages versus other encryption options, and how it might impact the existing block device stack. Also I need to identify any potential conflicts between these two drivers. What about performance characteristics, too? I'm already thinking about potential optimization strategies depending on the platform.
76/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config BLK_INLINE_ENCRYPTION" } Results: { "Output": "block/Kconfig=185=config BLK_SED_OPAL\n--\nblock/Kconfig-194-\nblock/Kconfig:195:config BLK_INLINE_ENCRYPTION\nblock/Kconfig-196-\tbool \"Enable inline encryption support in block layer\"\n--\nblock/Kconfig-201-\nblock/Kconfig:202:config BLK_INLINE_ENCRYPTION_FALLBACK\nblock/Kconfig-203-\tbool \"Enable crypto API fallback for blk-crypto\"\n" }
77/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 40096 output: 20 thoughts: 39 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Adding Encryption and Considering Filesystem Compatibility Alright, I'm thinking we need to introduce `BLK_INLINE_ENCRYPTION` and its fallback, `BLK_INLINE_ENCRYPTION_FALLBACK`. This seems like a natural progression, given the current discussion on enhancing security at the block level. We know we have users requesting this. My immediate next step, and it's a critical one, is to verify the interaction with `GFS2_FS`. I've got to ensure there's no inherent conflict or incompatibility there. We can't just slap this in without a thorough look at the filesystem's behavior. We know how sensitive these things are.
78/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config GFS2_FS" } Results: { "Output": "fs/gfs2/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/gfs2/Kconfig:2:config GFS2_FS\nfs/gfs2/Kconfig-3-\ttristate \"GFS2 file system support\"\n--\nfs/gfs2/Kconfig-26-\nfs/gfs2/Kconfig:27:config GFS2_FS_LOCKING_DLM\nfs/gfs2/Kconfig-28-\tbool \"GFS2 DLM locking\"\n" }
79/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 40457 output: 22 thoughts: 23 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Adding a Filesystem and a Persistent Memory Device Consideration Alright, the objective is to introduce a new filesystem, let's call it `GFS2_FS`. Fine, I'm noting that; it's a worthwhile addition. But before I get too deep into the implications of this, I need to consider all the pieces that are going to be affected, and how it will interact with existing systems. Now, hold on. Before I dive into `GFS2_FS`, I should probably also check the status of `BLK_DEV_PMEM`. Persistent memory devices are becoming more prevalent, and the interactions between filesystems and these memory technologies are complex and important. If these two things are going to interact, I'm going to want to make sure the interactions between them are clearly defined. I need to make sure I understand the full scope of how these things will integrate before making any architectural decisions.
80/2	2026/08/04 07:22	tool	grepper	0m Args: { "Expression": "config BLK_DEV_PMEM" } Results: { "Output": "drivers/nvdimm/Kconfig=17=if LIBNVDIMM\ndrivers/nvdimm/Kconfig-18-\ndrivers/nvdimm/Kconfig:19:config BLK_DEV_PMEM\ndrivers/nvdimm/Kconfig-20-\ttristate \"PMEM: Persistent memory block device support\"\n" }
81/2	2026/08/04 07:22	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 40804 output: 21 thoughts: 25 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Considering Persistent Memory Device Support Alright, the core work we're doing now revolves around persistent memory devices, specifically integrating them into the block layer. First thing on the docket, and probably the most crucial, is adding that `BLK_DEV_PMEM` define. This is the keystone, defining our support within the block layer itself. It's the flag we'll use to identify persistent memory devices within the core infrastructure. I need to make sure this is added correctly, that it aligns with our existing conventions, and doesn't introduce any conflicts with existing flags. Then, immediately following that, it's essential to confirm that our `VIRTIO_PMEM` driver setup is working. We need to assess how it works with the block layer; we want to ensure everything behaves as it should. We need to make sure we've properly hooked it up to leverage the persistent memory. I need to review the existing implementation and ensure it correctly handles the nuances of a persistent memory device within a virtualized environment, and confirm it leverages any new `BLK_DEV_PMEM` hooks.
82/2	2026/08/04 07:23	tool	grepper	0m Args: { "Expression": "config VIRTIO_PMEM" } Results: { "Output": "drivers/virtio/Kconfig=88=config VIRTIO_VDPA\n--\ndrivers/virtio/Kconfig-100-\ndrivers/virtio/Kconfig:101:config VIRTIO_PMEM\ndrivers/virtio/Kconfig-102-\ttristate \"Support for virtio pmem driver\"\n" }
83/2	2026/08/04 07:23	llm	patch-evaluator	0m Model: gemini-3.1-pro-preview Args: null Results: null Tokens: input: 41193 output: 492 thoughts: 651 Thoughts: Analyzing Block Layer Cgroup Association Changes Okay, let's add `VIRTIO_PMEM`. Now, let's dive into these configurations to ensure everything's properly enabled: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, `BTRFS_FS`, `MEMCG`, `BLK_DEV_THROTTLING`, `BLK_DEV_MD`, `BCACHE`, `BLK_DEV_DM`, `BLK_INLINE_ENCRYPTION`, `BLK_INLINE_ENCRYPTION_FALLBACK`, `GFS2_FS`, `BLK_DEV_PMEM`, and of course, `VIRTIO_PMEM` again. This is a pretty exhaustive list; it should cover all the code paths modified by the patch. Next, I need to understand the functional implications. Let's look at the key symbols: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, `bfq_bio_bfqg`, `blkcg_get_fc_appid`, `blkcg_set_ioprio`, `__blk_throtl_bio`, `bfqg_stats_update_legacy_io`, and `blk_cgroup_bio_start`. These are all the non-static functions this patch touches or introduces, and are highly relevant to what's changed. From what I can gather, this patch represents a core refactoring of the block layer's cgroup association logic. It's fundamentally changing how a `bio` is linked with a `blkcg` and `blkg`. The old `bio->bi_blkg` pointer is being replaced. New functions like `bio_blkg_lookup` and `bio_blkg` are introduced for lookup and pinning. This affects a whole host of subsystems: BFQ, iocost, iolatency, ioprio, throttle, bcache, dm, md, nvdimm, gfs2, and btrfs are all being updated to use this new API. Considering this touches the core block layer, and is reachable in virtualized environments, this is definitely a critical functional change that's prime for fuzzing. We need to validate this deeply. Alright, let's call the `set-results` tool now.
84/2	2026/08/04 07:23	tool	set-results	0m Args: { "EnableConfigs": [ "BLK_CGROUP", "BLK_CGROUP_IOLATENCY", "BLK_CGROUP_IOCOST", "BLK_CGROUP_IOPRIO", "IOSCHED_BFQ", "BFQ_GROUP_IOSCHED", "NVME_FC", "BLK_CGROUP_FC_APPID", "BTRFS_FS", "MEMCG", "BLK_DEV_THROTTLING", "BLK_DEV_MD", "BCACHE", "BLK_DEV_DM", "BLK_INLINE_ENCRYPTION", "BLK_INLINE_ENCRYPTION_FALLBACK", "GFS2_FS", "BLK_DEV_PMEM", "VIRTIO_PMEM" ], "FocusSymbols": [ "bio_blkg_lookup", "bio_blkg", "bio_associate_blkcg_from_css", "bio_associate_blkcg", "bio_clone_blkcg_association", "bio_put_blkg_ref", "blkcg_punt_bio_submit", "bfq_bio_bfqg", "blkcg_get_fc_appid", "blkcg_set_ioprio", "__blk_throtl_bio", "bfqg_stats_update_legacy_io", "blk_cgroup_bio_start" ], "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "BLK_CGROUP", "BLK_CGROUP_IOLATENCY", "BLK_CGROUP_IOCOST", "BLK_CGROUP_IOPRIO", "IOSCHED_BFQ", "BFQ_GROUP_IOSCHED", "NVME_FC", "BLK_CGROUP_FC_APPID", "BTRFS_FS", "MEMCG", "BLK_DEV_THROTTLING", "BLK_DEV_MD", "BCACHE", "BLK_DEV_DM", "BLK_INLINE_ENCRYPTION", "BLK_INLINE_ENCRYPTION_FALLBACK", "GFS2_FS", "BLK_DEV_PMEM", "VIRTIO_PMEM" ], "FocusSymbols": [ "bio_blkg_lookup", "bio_blkg", "bio_associate_blkcg_from_css", "bio_associate_blkcg", "bio_clone_blkcg_association", "bio_put_blkg_ref", "blkcg_punt_bio_submit", "bfq_bio_bfqg", "blkcg_get_fc_appid", "blkcg_set_ioprio", "__blk_throtl_bio", "bfqg_stats_update_legacy_io", "blk_cgroup_bio_start" ], "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.", "WorthFuzzing": true }

Trajectory: (Expand/Collapse All)

Seq

Timestamp

Type

Name

Duration

0/0

2026/08/04 07:16

flow

patch-triage

Args:

null

Results:

{
  "EnableConfigs": [
    "BLK_CGROUP",
    "BLK_CGROUP_IOLATENCY",
    "BLK_CGROUP_IOCOST",
    "BLK_CGROUP_IOPRIO",
    "IOSCHED_BFQ",
    "BFQ_GROUP_IOSCHED",
    "NVME_FC",
    "BLK_CGROUP_FC_APPID",
    "BTRFS_FS",
    "MEMCG",
    "BLK_DEV_THROTTLING",
    "BLK_DEV_MD",
    "BCACHE",
    "BLK_DEV_DM",
    "BLK_INLINE_ENCRYPTION",
    "BLK_INLINE_ENCRYPTION_FALLBACK",
    "GFS2_FS",
    "BLK_DEV_PMEM",
    "VIRTIO_PMEM"
  ],
  "FocusSymbols": [
    "bio_blkg_lookup",
    "bio_blkg",
    "bio_associate_blkcg_from_css",
    "bio_associate_blkcg",
    "bio_clone_blkcg_association",
    "bio_put_blkg_ref",
    "blkcg_punt_bio_submit",
    "bfq_bio_bfqg",
    "blkcg_get_fc_appid",
    "blkcg_set_ioprio",
    "__blk_throtl_bio",
    "bfqg_stats_update_legacy_io",
    "blk_cgroup_bio_start"
  ],
  "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.",
  "WorthFuzzing": true
}

1/1

2026/08/04 07:16

action

read-patch-diff

Args:

null

Results:

{
  "PatchDiff": "commit 37ab22cb5f20111358288fbe1554a0d2e13b1a8a\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Aug 4 07:16:16 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst\nindex 14b8c571c0d14..bbd79931d5ab5 100644\n--- a/Documentation/admin-guide/cgroup-v2.rst\n+++ b/Documentation/admin-guide/cgroup-v2.rst\n@@ -3235,7 +3235,7 @@ the configuration, the bio may be executed at a lower priority and if\n the writeback session is holding shared resources, e.g. a journal\n entry, may lead to priority inversion.  There is no one easy solution\n for the problem.  Filesystems can try to work around specific problem\n-cases by skipping wbc_init_bio() and using bio_associate_blkg()\n+cases by skipping wbc_init_bio() and using bio_associate_blkcg()\n directly.\n \n \ndiff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c\nindex e82ff03bda02e..3ac3b4c054026 100644\n--- a/block/bfq-cgroup.c\n+++ b/block/bfq-cgroup.c\n@@ -363,11 +363,13 @@ void bfqg_and_blkg_put(struct bfq_group *bfqg)\n \n void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq)\n {\n-\tstruct bfq_group *bfqg = blkg_to_bfqg(rq-\u003ebio-\u003ebi_blkg);\n+\tstruct blkcg_gq *blkg = bio_blkg_lookup(rq-\u003ebio);\n+\tstruct bfq_group *bfqg;\n \n-\tif (!bfqg)\n+\tif (!blkg)\n \t\treturn;\n \n+\tbfqg = blkg_to_bfqg(blkg);\n \tblkg_rwstat_add(\u0026bfqg-\u003estats.bytes, rq-\u003ecmd_flags, blk_rq_bytes(rq));\n \tblkg_rwstat_add(\u0026bfqg-\u003estats.ios, rq-\u003ecmd_flags, 1);\n }\n@@ -606,7 +608,7 @@ static void bfq_link_bfqg(struct bfq_data *bfqd, struct bfq_group *bfqg)\n \n struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)\n {\n-\tstruct blkcg_gq *blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq *blkg = bio_blkg_lookup(bio);\n \tstruct bfq_group *bfqg;\n \n \twhile (blkg) {\n@@ -614,14 +616,16 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)\n \t\t\tblkg = blkg-\u003eparent;\n \t\t\tcontinue;\n \t\t}\n+\n \t\tbfqg = blkg_to_bfqg(blkg);\n \t\tif (bfqg-\u003epd.online) {\n-\t\t\tbio_associate_blkg_from_css(bio, \u0026blkg-\u003eblkcg-\u003ecss);\n+\t\t\tbio_associate_blkcg_from_css(bio, \u0026blkg-\u003eblkcg-\u003ecss);\n \t\t\treturn bfqg;\n \t\t}\n \t\tblkg = blkg-\u003eparent;\n \t}\n-\tbio_associate_blkg_from_css(bio,\n+\n+\tbio_associate_blkcg_from_css(bio,\n \t\t\t\t\u0026bfqg_to_blkg(bfqd-\u003eroot_group)-\u003eblkcg-\u003ecss);\n \treturn bfqd-\u003eroot_group;\n }\ndiff --git a/block/bfq-iosched.c b/block/bfq-iosched.c\nindex 0f75301b3115f..3d51d743552cb 100644\n--- a/block/bfq-iosched.c\n+++ b/block/bfq-iosched.c\n@@ -128,6 +128,7 @@\n \n #include \"elevator.h\"\n #include \"blk.h\"\n+#include \"blk-cgroup.h\"\n #include \"blk-mq.h\"\n #include \"blk-mq-sched.h\"\n #include \"bfq-iosched.h\"\n@@ -2452,15 +2453,15 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,\n \tstruct request *free = NULL;\n \tbool ret;\n \n+#ifdef CONFIG_BFQ_GROUP_IOSCHED\n+\tif (bic \u0026\u0026 bio_blkg_lookup(bio) == NULL)\n+\t\treturn false;\n+#endif\n+\n \tspin_lock_irq(\u0026bfqd-\u003elock);\n \n \tif (bic) {\n-\t\t/*\n-\t\t * Make sure cgroup info is uptodate for current process before\n-\t\t * considering the merge.\n-\t\t */\n \t\tbfq_bic_update_cgroup(bic, bio);\n-\n \t\tbfqd-\u003ebio_bfqq = bic_to_bfqq(bic, op_is_sync(bio-\u003ebi_opf),\n \t\t\t\t\t     bfq_actuator_index(bfqd, bio));\n \t} else {\n@@ -6245,6 +6246,13 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,\n \tLIST_HEAD(free);\n \n #ifdef CONFIG_BFQ_GROUP_IOSCHED\n+\t/*\n+\t * Pin the blkg used to look up bfqg.  If this is the first IO for\n+\t * the blkcg on this queue, create the bfqg before holding bfqd-\u003elock.\n+\t */\n+\tif (rq-\u003ebio \u0026\u0026 !bio_flagged(rq-\u003ebio, BIO_BLKG_REF))\n+\t\tbio_blkg(rq-\u003ebio);\n+\n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys) \u0026\u0026 rq-\u003ebio)\n \t\tbfqg_stats_update_legacy_io(q, rq);\n #endif\ndiff --git a/block/bio.c b/block/bio.c\nindex 6a2f6fc3413e8..db33c993c2964 100644\n--- a/block/bio.c\n+++ b/block/bio.c\n@@ -179,12 +179,7 @@ static inline gfp_t try_alloc_gfp(gfp_t gfp)\n \n void bio_uninit(struct bio *bio)\n {\n-#ifdef CONFIG_BLK_CGROUP\n-\tif (bio-\u003ebi_blkg) {\n-\t\tblkg_put(bio-\u003ebi_blkg);\n-\t\tbio-\u003ebi_blkg = NULL;\n-\t}\n-#endif\n+\tbio_clear_blkcg(bio);\n \tif (bio_integrity(bio))\n \t\tbio_integrity_free(bio);\n \n@@ -233,10 +228,10 @@ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,\n \tbio-\u003ebi_end_io = NULL;\n \tbio-\u003ebi_private = NULL;\n #ifdef CONFIG_BLK_CGROUP\n-\tbio-\u003ebi_blkg = NULL;\n+\tbio-\u003ebi_blkcg = NULL;\n \tbio-\u003eissue_time_ns = 0;\n \tif (bdev)\n-\t\tbio_associate_blkg(bio);\n+\t\tbio_associate_blkcg(bio);\n #ifdef CONFIG_BLK_CGROUP_IOCOST\n \tbio-\u003ebi_iocost_cost = 0;\n #endif\n@@ -281,7 +276,7 @@ void bio_reset(struct bio *bio, struct block_device *bdev, blk_opf_t opf)\n \tbio-\u003ebi_io_vec = bv;\n \tbio-\u003ebi_bdev = bdev;\n \tif (bio-\u003ebi_bdev)\n-\t\tbio_associate_blkg(bio);\n+\t\tbio_associate_blkcg(bio);\n \tbio-\u003ebi_opf = opf;\n }\n EXPORT_SYMBOL(bio_reset);\n@@ -865,7 +860,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)\n \t\tif (bio-\u003ebi_bdev == bio_src-\u003ebi_bdev \u0026\u0026\n \t\t    bio_flagged(bio_src, BIO_REMAPPED))\n \t\t\tbio_set_flag(bio, BIO_REMAPPED);\n-\t\tbio_clone_blkg_association(bio, bio_src);\n+\t\tbio_clone_blkcg_association(bio, bio_src);\n \t}\n \n \tif (bio_crypt_clone(bio, bio_src, gfp) \u003c 0)\n@@ -1803,17 +1798,12 @@ void bio_endio(struct bio *bio)\n \t\tgoto again;\n \t}\n \n-#ifdef CONFIG_BLK_CGROUP\n \t/*\n \t * Release cgroup info.  We shouldn't have to do this here, but quite\n \t * a few callers of bio_init fail to call bio_uninit, so we cover up\n \t * for that here at least for now.\n \t */\n-\tif (bio-\u003ebi_blkg) {\n-\t\tblkg_put(bio-\u003ebi_blkg);\n-\t\tbio-\u003ebi_blkg = NULL;\n-\t}\n-#endif\n+\tbio_clear_blkcg(bio);\n \n \tif (bio-\u003ebi_end_io)\n \t\tbio-\u003ebi_end_io(bio);\ndiff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c\nindex 3ec21333f393b..7589c62099898 100644\n--- a/block/blk-cgroup-fc-appid.c\n+++ b/block/blk-cgroup-fc-appid.c\n@@ -50,8 +50,14 @@ EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);\n  */\n char *blkcg_get_fc_appid(struct bio *bio)\n {\n-\tif (!bio-\u003ebi_blkg || bio-\u003ebi_blkg-\u003eblkcg-\u003efc_app_id[0] == '\\0')\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n+\n+\tif (!blkcg)\n+\t\treturn NULL;\n+\n+\tif (blkcg-\u003efc_app_id[0] == '\\0')\n \t\treturn NULL;\n-\treturn bio-\u003ebi_blkg-\u003eblkcg-\u003efc_app_id;\n+\n+\treturn blkcg-\u003efc_app_id;\n }\n EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);\ndiff --git a/block/blk-cgroup.c b/block/blk-cgroup.c\nindex d9676126c5b5d..a70f92f1541b1 100644\n--- a/block/blk-cgroup.c\n+++ b/block/blk-cgroup.c\n@@ -170,10 +170,6 @@ static void __blkg_release(struct rcu_head *rcu)\n {\n \tstruct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);\n \n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tWARN_ON(!bio_list_empty(\u0026blkg-\u003easync_bios));\n-#endif\n-\n \tblkg_free(blkg);\n }\n \n@@ -206,19 +202,18 @@ static void blkg_release(struct percpu_ref *ref)\n #ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n static struct workqueue_struct *blkcg_punt_bio_wq;\n \n-static void blkg_async_bio_workfn(struct work_struct *work)\n+static void blkcg_async_bio_workfn(struct work_struct *work)\n {\n-\tstruct blkcg_gq *blkg = container_of(work, struct blkcg_gq,\n-\t\t\t\t\t     async_bio_work);\n+\tstruct blkcg *blkcg = container_of(work, struct blkcg, async_bio_work);\n \tstruct bio_list bios = BIO_EMPTY_LIST;\n \tstruct bio *bio;\n \tstruct blk_plug plug;\n \tbool need_plug = false;\n \n-\t/* as long as there are pending bios, @blkg can't go away */\n-\tspin_lock(\u0026blkg-\u003easync_bio_lock);\n-\tbio_list_merge_init(\u0026bios, \u0026blkg-\u003easync_bios);\n-\tspin_unlock(\u0026blkg-\u003easync_bio_lock);\n+\t/* as long as there are pending bios, @blkcg can't go away */\n+\tspin_lock(\u0026blkcg-\u003easync_bio_lock);\n+\tbio_list_merge_init(\u0026bios, \u0026blkcg-\u003easync_bios);\n+\tspin_unlock(\u0026blkcg-\u003easync_bio_lock);\n \n \t/* start plug only when bio_list contains at least 2 bios */\n \tif (bios.head \u0026\u0026 bios.head-\u003ebi_next) {\n@@ -239,15 +234,15 @@ static void blkg_async_bio_workfn(struct work_struct *work)\n  */\n void blkcg_punt_bio_submit(struct bio *bio)\n {\n-\tstruct blkcg_gq *blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n \n-\tif (blkg-\u003eparent) {\n-\t\tspin_lock(\u0026blkg-\u003easync_bio_lock);\n-\t\tbio_list_add(\u0026blkg-\u003easync_bios, bio);\n-\t\tspin_unlock(\u0026blkg-\u003easync_bio_lock);\n-\t\tqueue_work(blkcg_punt_bio_wq, \u0026blkg-\u003easync_bio_work);\n+\tif (blkcg \u0026\u0026 cgroup_parent(blkcg-\u003ecss.cgroup)) {\n+\t\tspin_lock(\u0026blkcg-\u003easync_bio_lock);\n+\t\tbio_list_add(\u0026blkcg-\u003easync_bios, bio);\n+\t\tspin_unlock(\u0026blkcg-\u003easync_bio_lock);\n+\t\tqueue_work(blkcg_punt_bio_wq, \u0026blkcg-\u003easync_bio_work);\n \t} else {\n-\t\t/* never bounce for the root cgroup */\n+\t\t/* Never bounce if there is no non-root blkcg to queue on. */\n \t\tsubmit_bio(bio);\n \t}\n }\n@@ -275,9 +270,9 @@ subsys_initcall(blkcg_punt_bio_init);\n  */\n struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)\n {\n-\tif (!bio || !bio-\u003ebi_blkg)\n+\tif (!bio || !bio_blkcg(bio))\n \t\treturn NULL;\n-\treturn \u0026bio-\u003ebi_blkg-\u003eblkcg-\u003ecss;\n+\treturn \u0026bio_blkcg(bio)-\u003ecss;\n }\n EXPORT_SYMBOL_GPL(bio_blkcg_css);\n \n@@ -325,11 +320,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,\n \tINIT_LIST_HEAD(\u0026blkg-\u003eq_node);\n \tblkg-\u003eblkcg = blkcg;\n \tblkg-\u003eiostat.blkg = blkg;\n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tspin_lock_init(\u0026blkg-\u003easync_bio_lock);\n-\tbio_list_init(\u0026blkg-\u003easync_bios);\n-\tINIT_WORK(\u0026blkg-\u003easync_bio_work, blkg_async_bio_workfn);\n-#endif\n \n \tu64_stats_init(\u0026blkg-\u003eiostat.sync);\n \tfor_each_possible_cpu(cpu) {\n@@ -1357,6 +1347,9 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)\n \n \tmutex_unlock(\u0026blkcg_pol_mutex);\n \n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tWARN_ON(!bio_list_empty(\u0026blkcg-\u003easync_bios));\n+#endif\n \tfree_percpu(blkcg-\u003elhead);\n \tkfree(blkcg);\n }\n@@ -1406,6 +1399,11 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)\n \trefcount_set(\u0026blkcg-\u003eonline_pin, 1);\n \tINIT_RADIX_TREE(\u0026blkcg-\u003eblkg_tree, GFP_NOWAIT);\n \tINIT_HLIST_HEAD(\u0026blkcg-\u003eblkg_list);\n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tspin_lock_init(\u0026blkcg-\u003easync_bio_lock);\n+\tbio_list_init(\u0026blkcg-\u003easync_bios);\n+\tINIT_WORK(\u0026blkcg-\u003easync_bio_work, blkcg_async_bio_workfn);\n+#endif\n #ifdef CONFIG_CGROUP_WRITEBACK\n \tINIT_LIST_HEAD(\u0026blkcg-\u003ecgwb_list);\n #endif\n@@ -2046,129 +2044,181 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)\n \tatomic64_add(delta, \u0026blkg-\u003edelay_nsec);\n }\n \n-static inline struct blkcg_gq *blkg_lookup_tryget(struct blkcg_gq *blkg)\n+/*\n+ * Return the blkg pinned by @bio through BIO_BLKG_REF.  The returned blkg is\n+ * already owned by @bio and no extra reference is acquired.  If the pinned\n+ * blkg can't be found, fall back to the root blkg.\n+ */\n+static struct blkcg_gq *bio_pinned_blkg(struct bio *bio)\n {\n-retry:\n-\tif (blkg_tryget(blkg))\n-\t\treturn blkg;\n+\tstruct request_queue *q = bdev_get_queue(bio-\u003ebi_bdev);\n+\tstruct blkcg_gq *blkg;\n \n-\tblkg = blkg-\u003eparent;\n-\tif (blkg)\n-\t\tgoto retry;\n+\trcu_read_lock();\n+\tblkg = blkg_lookup(bio_blkcg(bio), q);\n+\trcu_read_unlock();\n \n-\treturn NULL;\n+\tif (WARN_ON_ONCE(!blkg))\n+\t\treturn q-\u003eroot_blkg;\n+\treturn blkg;\n }\n+\n /**\n- * blkg_tryget_closest - try and get a blkg ref on the closet blkg\n+ * bio_blkg_lookup - look up a blkg associated with a bio\n  * @bio: target bio\n- * @css: target css\n  *\n- * As the failure mode here is to walk up the blkg tree, this ensure that the\n- * blkg-\u003eparent pointers are always valid.  This returns the blkg that it ended\n- * up taking a reference on or %NULL if no reference was taken.\n+ * Look up the queue-local blkg for @bio's current device and blkcg without\n+ * creating a missing blkg.  The first successful lookup pins the blkg to @bio;\n+ * later lookups reuse the bio-owned reference.\n  */\n-static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,\n-\t\tstruct cgroup_subsys_state *css)\n+struct blkcg_gq *bio_blkg_lookup(struct bio *bio)\n {\n-\tstruct request_queue *q = bio-\u003ebi_bdev-\u003ebd_queue;\n-\tstruct blkcg *blkcg = css_to_blkcg(css);\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n+\tstruct request_queue *q;\n \tstruct blkcg_gq *blkg;\n \n+\tif (bio_flagged(bio, BIO_BLKG_REF))\n+\t\treturn bio_pinned_blkg(bio);\n+\n+\tif (!blkcg || !bio-\u003ebi_bdev)\n+\t\treturn NULL;\n+\n+\tq = bdev_get_queue(bio-\u003ebi_bdev);\n \trcu_read_lock();\n \tblkg = blkg_lookup(blkcg, q);\n-\tif (likely(blkg))\n-\t\tblkg = blkg_lookup_tryget(blkg);\n+\tif (blkg \u0026\u0026 blkg_tryget(blkg))\n+\t\tbio_set_flag(bio, BIO_BLKG_REF);\n+\telse\n+\t\tblkg = NULL;\n \trcu_read_unlock();\n \n-\tif (blkg)\n-\t\treturn blkg;\n+\treturn blkg;\n+}\n+EXPORT_SYMBOL_GPL(bio_blkg_lookup);\n+\n+/**\n+ * bio_put_blkg_ref - drop the blkg reference pinned by a bio\n+ * @bio: target bio\n+ *\n+ * Drop the bio-owned blkg reference acquired by bio_blkg(), if any.\n+ */\n+void bio_put_blkg_ref(struct bio *bio)\n+{\n+\tif (bio_flagged(bio, BIO_BLKG_REF)) {\n+\t\tstruct blkcg_gq *blkg = bio_pinned_blkg(bio);\n+\n+\t\tblkg_put(blkg);\n+\t\tbio_clear_flag(bio, BIO_BLKG_REF);\n+\t}\n+}\n+EXPORT_SYMBOL_GPL(bio_put_blkg_ref);\n+\n+/**\n+ * bio_blkg - look up the blkg associated with a bio\n+ * @bio: target bio\n+ *\n+ * Look up the queue-local blkg for @bio's current device and blkcg.  If this\n+ * is the first policy use of @bio, create the missing blkg hierarchy if\n+ * necessary, pin the exact blkg, and mark @bio so bio_clear_blkcg() can drop\n+ * the reference when the bio completes.\n+ */\n+struct blkcg_gq *bio_blkg(struct bio *bio)\n+{\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n+\tstruct gendisk *disk;\n+\tstruct request_queue *q;\n+\tstruct blkcg_gq *blkg;\n+\n+\tif (!blkcg || !bio-\u003ebi_bdev)\n+\t\treturn NULL;\n+\n+\tif (bio_flagged(bio, BIO_BLKG_REF))\n+\t\treturn bio_pinned_blkg(bio);\n+\n+\tdisk = bio-\u003ebi_bdev-\u003ebd_disk;\n+\tq = disk-\u003equeue;\n \n-\t/*\n-\t * Fast path failed, we're probably issuing IO in this cgroup the first\n-\t * time, hold lock to create new blkg.\n-\t */\n \tspin_lock_irq(\u0026q-\u003equeue_lock);\n-\tblkg = blkg_lookup_create(blkcg, bio-\u003ebi_bdev-\u003ebd_disk);\n-\tif (blkg)\n-\t\tblkg = blkg_lookup_tryget(blkg);\n+\tblkg = blkg_lookup_create(blkcg, disk);\n+\tif (blkg \u0026\u0026 blkg-\u003eblkcg == blkcg \u0026\u0026 blkg_tryget(blkg))\n+\t\tbio_set_flag(bio, BIO_BLKG_REF);\n+\telse\n+\t\tblkg = NULL;\n \tspin_unlock_irq(\u0026q-\u003equeue_lock);\n \n \treturn blkg;\n }\n+EXPORT_SYMBOL_GPL(bio_blkg);\n \n /**\n- * bio_associate_blkg_from_css - associate a bio with a specified css\n+ * bio_associate_blkcg_from_css - associate a bio with a specified css\n  * @bio: target bio\n  * @css: target css\n  *\n- * Associate @bio with the blkg found by combining the css's blkg and the\n- * request_queue of the @bio.  An association failure is handled by walking up\n- * the blkg tree.  Therefore, the blkg associated can be anything between @blkg\n- * and q-\u003eroot_blkg.  This situation only happens when a cgroup is dying and\n- * then the remaining bios will spill to the closest alive blkg.\n+ * Associate @bio with the blkcg found from @css.  The queue-local blkg is\n+ * created and pinned by bio_blkg() when blkcg policies need it.\n  *\n- * A reference will be taken on the blkg and will be released when @bio is\n+ * A reference will be taken on the blkcg and will be released when @bio is\n  * freed.\n  */\n-void bio_associate_blkg_from_css(struct bio *bio,\n+void bio_associate_blkcg_from_css(struct bio *bio,\n \t\t\t\t struct cgroup_subsys_state *css)\n {\n-\tif (bio-\u003ebi_blkg)\n-\t\tblkg_put(bio-\u003ebi_blkg);\n+\tstruct blkcg *blkcg;\n \n-\tif (css \u0026\u0026 css-\u003eparent) {\n-\t\tbio-\u003ebi_blkg = blkg_tryget_closest(bio, css);\n-\t} else {\n-\t\tblkg_get(bdev_get_queue(bio-\u003ebi_bdev)-\u003eroot_blkg);\n-\t\tbio-\u003ebi_blkg = bdev_get_queue(bio-\u003ebi_bdev)-\u003eroot_blkg;\n-\t}\n+\tif (!css || !css-\u003eparent)\n+\t\tcss = \u0026blkcg_root.css;\n+\n+\tblkcg = css_to_blkcg(css);\n+\tif (bio_blkcg(bio) == blkcg)\n+\t\treturn;\n+\n+\tcss_get(css);\n+\tbio_clear_blkcg(bio);\n+\tbio-\u003ebi_blkcg = blkcg;\n }\n-EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);\n+EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css);\n \n /**\n- * bio_associate_blkg - associate a bio with a blkg\n+ * bio_associate_blkcg - associate a bio with a blkcg\n  * @bio: target bio\n  *\n- * Associate @bio with the blkg found from the bio's css and request_queue.\n- * If one is not found, bio_lookup_blkg() creates the blkg.  If a blkg is\n- * already associated, the css is reused and association redone as the\n- * request_queue may have changed.\n+ * Associate @bio with the blkcg found from the bio's css.  If a blkcg is\n+ * already associated, keep it as blkcg association is not queue-local.\n  */\n-void bio_associate_blkg(struct bio *bio)\n+void bio_associate_blkcg(struct bio *bio)\n {\n \tstruct cgroup_subsys_state *css;\n \n \tif (blk_op_is_passthrough(bio-\u003ebi_opf))\n \t\treturn;\n \n-\tif (bio-\u003ebi_blkg) {\n-\t\tcss = bio_blkcg_css(bio);\n-\t\tbio_associate_blkg_from_css(bio, css);\n-\t} else {\n-\t\trcu_read_lock();\n-\t\tcss = blkcg_css();\n-\t\tif (!css_tryget_online(css))\n-\t\t\tcss = NULL;\n-\t\trcu_read_unlock();\n+\tif (bio_blkcg(bio))\n+\t\treturn;\n \n-\t\tbio_associate_blkg_from_css(bio, css);\n-\t\tif (css)\n-\t\t\tcss_put(css);\n-\t}\n+\trcu_read_lock();\n+\tcss = blkcg_css();\n+\tif (!css_tryget_online(css))\n+\t\tcss = NULL;\n+\trcu_read_unlock();\n+\n+\tbio_associate_blkcg_from_css(bio, css);\n+\tif (css)\n+\t\tcss_put(css);\n }\n-EXPORT_SYMBOL_GPL(bio_associate_blkg);\n+EXPORT_SYMBOL_GPL(bio_associate_blkcg);\n \n /**\n- * bio_clone_blkg_association - clone blkg association from src to dst bio\n+ * bio_clone_blkcg_association - clone blkcg association from src to dst bio\n  * @dst: destination bio\n  * @src: source bio\n  */\n-void bio_clone_blkg_association(struct bio *dst, struct bio *src)\n+void bio_clone_blkcg_association(struct bio *dst, struct bio *src)\n {\n-\tif (src-\u003ebi_blkg)\n-\t\tbio_associate_blkg_from_css(dst, bio_blkcg_css(src));\n+\tif (bio_blkcg(src))\n+\t\tbio_associate_blkcg_from_css(dst, bio_blkcg_css(src));\n }\n-EXPORT_SYMBOL_GPL(bio_clone_blkg_association);\n+EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);\n \n static int blk_cgroup_io_type(struct bio *bio)\n {\n@@ -2181,20 +2231,27 @@ static int blk_cgroup_io_type(struct bio *bio)\n \n void blk_cgroup_bio_start(struct bio *bio)\n {\n-\tstruct blkcg *blkcg = bio-\u003ebi_blkg-\u003eblkcg;\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n+\tstruct blkcg_gq *blkg;\n \tint rwd = blk_cgroup_io_type(bio), cpu;\n \tstruct blkg_iostat_set *bis;\n \tunsigned long flags;\n \n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys))\n \t\treturn;\n+\tif (!blkcg)\n+\t\treturn;\n \n \t/* Root-level stats are sourced from system-wide IO stats */\n \tif (!cgroup_parent(blkcg-\u003ecss.cgroup))\n \t\treturn;\n \n+\tblkg = bio_blkg_lookup(bio);\n+\tif (!blkg)\n+\t\treturn;\n+\n \tcpu = get_cpu();\n-\tbis = per_cpu_ptr(bio-\u003ebi_blkg-\u003eiostat_cpu, cpu);\n+\tbis = per_cpu_ptr(blkg-\u003eiostat_cpu, cpu);\n \tflags = u64_stats_update_begin_irqsave(\u0026bis-\u003esync);\n \n \t/*\ndiff --git a/block/blk-cgroup.h b/block/blk-cgroup.h\nindex 615390f751aa2..b457c2b4ac7c8 100644\n--- a/block/blk-cgroup.h\n+++ b/block/blk-cgroup.h\n@@ -73,14 +73,7 @@ struct blkcg_gq {\n \tstruct blkg_iostat_set\t\tiostat;\n \n \tstruct blkg_policy_data\t\t*pd[BLKCG_MAX_POLS];\n-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n-\tspinlock_t\t\t\tasync_bio_lock;\n-\tstruct bio_list\t\t\tasync_bios;\n-#endif\n-\tunion {\n-\t\tstruct work_struct\tasync_bio_work;\n-\t\tstruct work_struct\tfree_work;\n-\t};\n+\tstruct work_struct\t\tfree_work;\n \n \tatomic_t\t\t\tuse_delay;\n \tatomic64_t\t\t\tdelay_nsec;\n@@ -111,6 +104,11 @@ struct blkcg {\n \t */\n \tstruct llist_head __percpu\t*lhead;\n \n+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO\n+\tspinlock_t\t\t\tasync_bio_lock;\n+\tstruct bio_list\t\t\tasync_bios;\n+\tstruct work_struct\t\tasync_bio_work;\n+#endif\n #ifdef CONFIG_BLK_CGROUP_FC_APPID\n \tchar                            fc_app_id[FC_APPID_LEN];\n #endif\n@@ -124,6 +122,11 @@ static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)\n \treturn css ? container_of(css, struct blkcg, css) : NULL;\n }\n \n+static inline struct blkcg *bio_blkcg(struct bio *bio)\n+{\n+\treturn bio-\u003ebi_blkcg;\n+}\n+\n /*\n  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a\n  * request_queue (q).  This is used by blkcg policies which need to track\n@@ -276,6 +279,9 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,\n \treturn blkg;\n }\n \n+struct blkcg_gq *bio_blkg_lookup(struct bio *bio);\n+struct blkcg_gq *bio_blkg(struct bio *bio);\n+\n /**\n  * blkg_to_pd - get policy private data\n  * @blkg: blkg of interest\n@@ -343,6 +349,18 @@ static inline void blkg_put(struct blkcg_gq *blkg)\n \tpercpu_ref_put(\u0026blkg-\u003erefcnt);\n }\n \n+static inline void bio_clear_blkcg(struct bio *bio)\n+{\n+\tstruct blkcg *blkcg = bio_blkcg(bio);\n+\n+\tbio_put_blkg_ref(bio);\n+\n+\tif (blkcg) {\n+\t\tcss_put(\u0026blkcg-\u003ecss);\n+\t\tbio-\u003ebi_blkcg = NULL;\n+\t}\n+}\n+\n /**\n  * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants\n  * @d_blkg: loop cursor pointing to the current descendant\n@@ -455,7 +473,7 @@ static inline void blkcg_clear_delay(struct blkcg_gq *blkg)\n  */\n static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio)\n {\n-\treturn rq-\u003ebio-\u003ebi_blkg == bio-\u003ebi_blkg \u0026\u0026\n+\treturn bio_blkcg(rq-\u003ebio) == bio_blkcg(bio) \u0026\u0026\n \t\tbio_issue_as_root_blkg(rq-\u003ebio) == bio_issue_as_root_blkg(bio);\n }\n \n@@ -481,6 +499,9 @@ struct blkcg_policy {\n struct blkcg {\n };\n \n+static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }\n+static inline struct blkcg_gq *bio_blkg_lookup(struct bio *bio) { return NULL; }\n+static inline struct blkcg_gq *bio_blkg(struct bio *bio) { return NULL; }\n static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }\n static inline void blkg_init_queue(struct request_queue *q) { }\n static inline int blkcg_init_disk(struct gendisk *disk) { return 0; }\n@@ -497,6 +518,7 @@ static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,\n static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }\n static inline void blkg_get(struct blkcg_gq *blkg) { }\n static inline void blkg_put(struct blkcg_gq *blkg) { }\n+static inline void bio_clear_blkcg(struct bio *bio) { }\n static inline void blk_cgroup_bio_start(struct bio *bio) { }\n static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }\n \ndiff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c\nindex 2a5c52ab74b4c..5ef4baab444bb 100644\n--- a/block/blk-crypto-fallback.c\n+++ b/block/blk-crypto-fallback.c\n@@ -187,7 +187,7 @@ static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,\n \tbio-\u003ebi_write_hint\t= bio_src-\u003ebi_write_hint;\n \tbio-\u003ebi_write_stream\t= bio_src-\u003ebi_write_stream;\n \tbio-\u003ebi_iter.bi_sector\t= bio_src-\u003ebi_iter.bi_sector;\n-\tbio_clone_blkg_association(bio, bio_src);\n+\tbio_clone_blkcg_association(bio, bio_src);\n \n \t/*\n \t * Move page array up in the allocated memory for the bio vecs as far as\ndiff --git a/block/blk-iocost.c b/block/blk-iocost.c\nindex 8b2aeba2e1e39..62ffd759bb954 100644\n--- a/block/blk-iocost.c\n+++ b/block/blk-iocost.c\n@@ -2686,7 +2686,7 @@ iocg_handle_over_budget(struct rq_qos *rqos, struct ioc_gq *iocg,\n \n static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)\n {\n-\tstruct blkcg_gq *blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq *blkg = bio_blkg(bio);\n \tstruct ioc *ioc = rqos_to_ioc(rqos);\n \tstruct ioc_gq *iocg = blkg_to_iocg(blkg);\n \tstruct ioc_now now;\n@@ -2775,7 +2775,7 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)\n static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,\n \t\t\t   struct bio *bio)\n {\n-\tstruct ioc_gq *iocg = blkg_to_iocg(bio-\u003ebi_blkg);\n+\tstruct ioc_gq *iocg = blkg_to_iocg(bio_blkg_lookup(bio));\n \tstruct ioc *ioc = rqos_to_ioc(rqos);\n \tsector_t bio_end = bio_end_sector(bio);\n \tstruct ioc_now now;\n@@ -2833,9 +2833,13 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,\n \n static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)\n {\n-\tstruct ioc_gq *iocg = blkg_to_iocg(bio-\u003ebi_blkg);\n+\tstruct ioc_gq *iocg;\n+\n+\tif (!bio-\u003ebi_iocost_cost)\n+\t\treturn;\n \n-\tif (iocg \u0026\u0026 bio-\u003ebi_iocost_cost)\n+\tiocg = blkg_to_iocg(bio_blkg_lookup(bio));\n+\tif (iocg)\n \t\tatomic64_add(bio-\u003ebi_iocost_cost, \u0026iocg-\u003edone_vtime);\n }\n \ndiff --git a/block/blk-iolatency.c b/block/blk-iolatency.c\nindex cef02b6c5fa91..7ad18a538d7e2 100644\n--- a/block/blk-iolatency.c\n+++ b/block/blk-iolatency.c\n@@ -463,7 +463,7 @@ static void check_scale_change(struct iolatency_grp *iolat)\n static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)\n {\n \tstruct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);\n-\tstruct blkcg_gq *blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq *blkg = bio_blkg(bio);\n \tbool issue_as_root = bio_issue_as_root_blkg(bio);\n \n \tif (!blkiolat-\u003eenabled)\n@@ -590,11 +590,14 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)\n \tbool issue_as_root = bio_issue_as_root_blkg(bio);\n \tint inflight = 0;\n \n-\tblkg = bio-\u003ebi_blkg;\n-\tif (!blkg || !bio_flagged(bio, BIO_QOS_THROTTLED))\n+\tif (!bio_flagged(bio, BIO_QOS_THROTTLED))\n \t\treturn;\n \n-\tiolat = blkg_to_lat(bio-\u003ebi_blkg);\n+\tblkg = bio_blkg_lookup(bio);\n+\tif (!blkg)\n+\t\treturn;\n+\n+\tiolat = blkg_to_lat(blkg);\n \tif (!iolat)\n \t\treturn;\n \ndiff --git a/block/blk-ioprio.c b/block/blk-ioprio.c\nindex 8fa8bca350629..5e3f8e49550da 100644\n--- a/block/blk-ioprio.c\n+++ b/block/blk-ioprio.c\n@@ -132,7 +132,7 @@ static struct blkcg_policy ioprio_policy = {\n \n void blkcg_set_ioprio(struct bio *bio)\n {\n-\tstruct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio-\u003ebi_blkg-\u003eblkcg);\n+\tstruct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio_blkcg(bio));\n \tu16 prio;\n \n \tif (!blkcg || blkcg-\u003eprio_policy == POLICY_NO_CHANGE)\ndiff --git a/block/blk-throttle.c b/block/blk-throttle.c\nindex ffc3b70065d4b..3828c38579002 100644\n--- a/block/blk-throttle.c\n+++ b/block/blk-throttle.c\n@@ -1792,7 +1792,7 @@ static bool tg_within_limit(struct throtl_grp *tg, struct bio *bio, bool rw)\n bool __blk_throtl_bio(struct bio *bio)\n {\n \tstruct request_queue *q = bdev_get_queue(bio-\u003ebi_bdev);\n-\tstruct blkcg_gq *blkg = bio-\u003ebi_blkg;\n+\tstruct blkcg_gq *blkg = bio_blkg(bio);\n \tstruct throtl_qnode *qn = NULL;\n \tstruct throtl_grp *tg = blkg_to_tg(blkg);\n \tstruct throtl_service_queue *sq;\ndiff --git a/block/blk-throttle.h b/block/blk-throttle.h\nindex 9d7a42c039a15..609a126c7ccb2 100644\n--- a/block/blk-throttle.h\n+++ b/block/blk-throttle.h\n@@ -173,7 +173,7 @@ static inline bool blk_should_throtl(struct bio *bio)\n \tif (!blk_throtl_activated(bio-\u003ebi_bdev-\u003ebd_queue))\n \t\treturn false;\n \n-\ttg = blkg_to_tg(bio-\u003ebi_blkg);\n+\ttg = blkg_to_tg(bio_blkg(bio));\n \tif (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {\n \t\tif (!bio_flagged(bio, BIO_CGROUP_ACCT)) {\n \t\t\tbio_set_flag(bio, BIO_CGROUP_ACCT);\ndiff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c\nindex 3fa3b13a410f4..c0f945b8d9413 100644\n--- a/drivers/md/bcache/request.c\n+++ b/drivers/md/bcache/request.c\n@@ -848,7 +848,7 @@ static CLOSURE_CALLBACK(cached_dev_read_done)\n \t\ts-\u003eiop.bio-\u003ebi_iter.bi_sector =\n \t\t\ts-\u003ecache_miss-\u003ebi_iter.bi_sector;\n \t\ts-\u003eiop.bio-\u003ebi_iter.bi_size = s-\u003einsert_bio_sectors \u003c\u003c 9;\n-\t\tbio_clone_blkg_association(s-\u003eiop.bio, s-\u003ecache_miss);\n+\t\tbio_clone_blkcg_association(s-\u003eiop.bio, s-\u003ecache_miss);\n \t\tbch_bio_map(s-\u003eiop.bio, NULL);\n \n \t\tbio_copy_data(s-\u003ecache_miss, s-\u003eiop.bio);\ndiff --git a/drivers/md/dm.c b/drivers/md/dm.c\nindex d413bfaf35278..cd68eec77f5a1 100644\n--- a/drivers/md/dm.c\n+++ b/drivers/md/dm.c\n@@ -1373,7 +1373,7 @@ void dm_submit_bio_remap(struct bio *clone, struct bio *tgt_clone)\n \tif (!tgt_clone)\n \t\ttgt_clone = clone;\n \n-\tbio_clone_blkg_association(tgt_clone, io-\u003eorig_bio);\n+\tbio_clone_blkcg_association(tgt_clone, io-\u003eorig_bio);\n \n \t/*\n \t * Account io-\u003eorigin_bio to DM dev on behalf of target\ndiff --git a/drivers/md/md.c b/drivers/md/md.c\nindex d1465bcd86c81..af55f8efa46bc 100644\n--- a/drivers/md/md.c\n+++ b/drivers/md/md.c\n@@ -9355,7 +9355,7 @@ void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,\n \t\treturn;\n \n \tbio_chain(discard_bio, bio);\n-\tbio_clone_blkg_association(discard_bio, bio);\n+\tbio_clone_blkcg_association(discard_bio, bio);\n \tmddev_trace_remap(mddev, discard_bio, bio-\u003ebi_iter.bi_sector);\n \tsubmit_bio_noacct(discard_bio);\n }\ndiff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c\nindex 4176046627beb..54e4adb0ccb7d 100644\n--- a/drivers/nvdimm/nd_virtio.c\n+++ b/drivers/nvdimm/nd_virtio.c\n@@ -121,7 +121,7 @@ int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)\n \n \t\tif (!child)\n \t\t\treturn -ENOMEM;\n-\t\tbio_clone_blkg_association(child, bio);\n+\t\tbio_clone_blkcg_association(child, bio);\n \t\tchild-\u003ebi_iter.bi_sector = -1;\n \t\tbio_chain(child, bio);\n \t\tsubmit_bio(child);\ndiff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c\nindex 6dabe73ad790d..6512dbd9516fc 100644\n--- a/fs/gfs2/lops.c\n+++ b/fs/gfs2/lops.c\n@@ -484,7 +484,7 @@ static struct bio *gfs2_chain_bio(struct bio *prev, unsigned int nr_iovecs,\n \tstruct bio *new;\n \n \tnew = bio_alloc(prev-\u003ebi_bdev, nr_iovecs, opf, GFP_NOIO);\n-\tbio_clone_blkg_association(new, prev);\n+\tbio_clone_blkcg_association(new, prev);\n \tnew-\u003ebi_iter.bi_sector = sector;\n \tbio_chain(new, prev);\n \tsubmit_bio(prev);\n@@ -1114,4 +1114,3 @@ const struct gfs2_log_operations *gfs2_log_ops[] = {\n \t\u0026gfs2_revoke_lops,\n \tNULL,\n };\n-\ndiff --git a/include/linux/bio.h b/include/linux/bio.h\nindex 8f33f717b14f5..e5799fdf431d2 100644\n--- a/include/linux/bio.h\n+++ b/include/linux/bio.h\n@@ -503,18 +503,20 @@ static inline void bio_release_pages(struct bio *bio, bool mark_dirty)\n \tdisk_devt((bio)-\u003ebi_bdev-\u003ebd_disk)\n \n #ifdef CONFIG_BLK_CGROUP\n-void bio_associate_blkg(struct bio *bio);\n-void bio_associate_blkg_from_css(struct bio *bio,\n+void bio_associate_blkcg(struct bio *bio);\n+void bio_associate_blkcg_from_css(struct bio *bio,\n \t\t\t\t struct cgroup_subsys_state *css);\n-void bio_clone_blkg_association(struct bio *dst, struct bio *src);\n+void bio_clone_blkcg_association(struct bio *dst, struct bio *src);\n+void bio_put_blkg_ref(struct bio *bio);\n void blkcg_punt_bio_submit(struct bio *bio);\n #else\t/* CONFIG_BLK_CGROUP */\n-static inline void bio_associate_blkg(struct bio *bio) { }\n-static inline void bio_associate_blkg_from_css(struct bio *bio,\n+static inline void bio_associate_blkcg(struct bio *bio) { }\n+static inline void bio_associate_blkcg_from_css(struct bio *bio,\n \t\t\t\t\t       struct cgroup_subsys_state *css)\n { }\n-static inline void bio_clone_blkg_association(struct bio *dst,\n+static inline void bio_clone_blkcg_association(struct bio *dst,\n \t\t\t\t\t      struct bio *src) { }\n+static inline void bio_put_blkg_ref(struct bio *bio) { }\n static inline void blkcg_punt_bio_submit(struct bio *bio)\n {\n \tsubmit_bio(bio);\n@@ -524,10 +526,12 @@ static inline void blkcg_punt_bio_submit(struct bio *bio)\n static inline void bio_set_dev(struct bio *bio, struct block_device *bdev)\n {\n \tbio_clear_flag(bio, BIO_REMAPPED);\n-\tif (bio-\u003ebi_bdev != bdev)\n+\tif (bio-\u003ebi_bdev != bdev) {\n+\t\tbio_put_blkg_ref(bio);\n \t\tbio_clear_flag(bio, BIO_BPS_THROTTLED);\n+\t}\n \tbio-\u003ebi_bdev = bdev;\n-\tbio_associate_blkg(bio);\n+\tbio_associate_blkcg(bio);\n }\n \n /*\ndiff --git a/include/linux/blk_types.h b/include/linux/blk_types.h\nindex 8808ee76e73c0..5f95c2e0e90b0 100644\n--- a/include/linux/blk_types.h\n+++ b/include/linux/blk_types.h\n@@ -246,12 +246,10 @@ struct bio {\n \tvoid\t\t\t*bi_private;\n #ifdef CONFIG_BLK_CGROUP\n \t/*\n-\t * Represents the association of the css and request_queue for the bio.\n-\t * If a bio goes direct to device, it will not have a blkg as it will\n-\t * not have a request_queue associated with it.  The reference is put\n-\t * on release of the bio.\n+\t * Represents the blkcg css association for the bio.  The reference is\n+\t * put on release of the bio.\n \t */\n-\tstruct blkcg_gq\t\t*bi_blkg;\n+\tstruct blkcg\t\t*bi_blkcg;\n \t/* Time that this bio was issued. */\n \tu64\t\t\tissue_time_ns;\n #ifdef CONFIG_BLK_CGROUP_IOCOST\n@@ -309,6 +307,7 @@ enum {\n \tBIO_TRACE_COMPLETION,\t/* bio_endio() should trace the final completion\n \t\t\t\t * of this bio. */\n \tBIO_CGROUP_ACCT,\t/* has been accounted to a cgroup */\n+\tBIO_BLKG_REF,\t\t/* bio pins the associated blkg */\n \tBIO_QOS_THROTTLED,\t/* bio went through rq_qos throttle path */\n \t/*\n \t * This bio has completed bps throttling at the single tg granularity,\ndiff --git a/include/linux/writeback.h b/include/linux/writeback.h\nindex 62552a2ce5b9e..4f869fe9cc90f 100644\n--- a/include/linux/writeback.h\n+++ b/include/linux/writeback.h\n@@ -262,7 +262,7 @@ static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)\n \t * regular writeback instead of writing things out itself.\n \t */\n \tif (wbc-\u003ewb)\n-\t\tbio_associate_blkg_from_css(bio, wbc-\u003ewb-\u003eblkcg_css);\n+\t\tbio_associate_blkcg_from_css(bio, wbc-\u003ewb-\u003eblkcg_css);\n }\n \n void inode_switch_wbs_work_fn(struct work_struct *work);\ndiff --git a/mm/page_io.c b/mm/page_io.c\nindex b23f494fcc83d..112e504756055 100644\n--- a/mm/page_io.c\n+++ b/mm/page_io.c\n@@ -316,7 +316,7 @@ static inline void count_swpout_vm_event(struct folio *folio)\n }\n \n #if defined(CONFIG_MEMCG) \u0026\u0026 defined(CONFIG_BLK_CGROUP)\n-static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)\n+static void bio_associate_blkcg_from_page(struct bio *bio, struct folio *folio)\n {\n \tstruct cgroup_subsys_state *css;\n \tstruct mem_cgroup *memcg;\n@@ -331,12 +331,12 @@ static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)\n \t\tcss = NULL;\n \trcu_read_unlock();\n \n-\tbio_associate_blkg_from_css(bio, css);\n+\tbio_associate_blkcg_from_css(bio, css);\n \tif (css)\n \t\tcss_put(css);\n }\n #else\n-#define bio_associate_blkg_from_page(bio, folio)\t\tdo { } while (0)\n+#define bio_associate_blkcg_from_page(bio, folio)\tdo { } while (0)\n #endif /* CONFIG_MEMCG \u0026\u0026 CONFIG_BLK_CGROUP */\n \n struct swap_iocb {\n@@ -436,7 +436,7 @@ static void swap_writepage_bdev_sync(struct folio *folio,\n \tbio.bi_iter.bi_sector = swap_folio_sector(folio);\n \tbio_add_folio_nofail(\u0026bio, folio, folio_size(folio), 0);\n \n-\tbio_associate_blkg_from_page(\u0026bio, folio);\n+\tbio_associate_blkcg_from_page(\u0026bio, folio);\n \tcount_swpout_vm_event(folio);\n \n \tfolio_start_writeback(folio);\n@@ -456,7 +456,7 @@ static void swap_writepage_bdev_async(struct folio *folio,\n \tbio-\u003ebi_end_io = end_swap_bio_write;\n \tbio_add_folio_nofail(bio, folio, folio_size(folio), 0);\n \n-\tbio_associate_blkg_from_page(bio, folio);\n+\tbio_associate_blkcg_from_page(bio, folio);\n \tcount_swpout_vm_event(folio);\n \tfolio_start_writeback(folio);\n \tfolio_unlock(folio);\n"
}

2/1

2026/08/04 07:16

agent

patch-evaluator

Model:

best-expensive

Args:

null

Results:

{
  "EnableConfigs": [
    "BLK_CGROUP",
    "BLK_CGROUP_IOLATENCY",
    "BLK_CGROUP_IOCOST",
    "BLK_CGROUP_IOPRIO",
    "IOSCHED_BFQ",
    "BFQ_GROUP_IOSCHED",
    "NVME_FC",
    "BLK_CGROUP_FC_APPID",
    "BTRFS_FS",
    "MEMCG",
    "BLK_DEV_THROTTLING",
    "BLK_DEV_MD",
    "BCACHE",
    "BLK_DEV_DM",
    "BLK_INLINE_ENCRYPTION",
    "BLK_INLINE_ENCRYPTION_FALLBACK",
    "GFS2_FS",
    "BLK_DEV_PMEM",
    "VIRTIO_PMEM"
  ],
  "FocusSymbols": [
    "bio_blkg_lookup",
    "bio_blkg",
    "bio_associate_blkcg_from_css",
    "bio_associate_blkcg",
    "bio_clone_blkcg_association",
    "bio_put_blkg_ref",
    "blkcg_punt_bio_submit",
    "bfq_bio_bfqg",
    "blkcg_get_fc_appid",
    "blkcg_set_ioprio",
    "__blk_throtl_bio",
    "bfqg_stats_update_legacy_io",
    "blk_cgroup_bio_start"
  ],
  "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.",
  "WorthFuzzing": true
}

Instruction:

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
  even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs
   output array, and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Prompt:

For your convenience, here is the diff of the changes:
commit 37ab22cb5f20111358288fbe1554a0d2e13b1a8a
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Aug 4 07:16:16 2026 +0000

    syz-cluster: applied patch under review

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 14b8c571c0d14..bbd79931d5ab5 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -3235,7 +3235,7 @@ the configuration, the bio may be executed at a lower priority and if
 the writeback session is holding shared resources, e.g. a journal
 entry, may lead to priority inversion.  There is no one easy solution
 for the problem.  Filesystems can try to work around specific problem
-cases by skipping wbc_init_bio() and using bio_associate_blkg()
+cases by skipping wbc_init_bio() and using bio_associate_blkcg()
 directly.
 
 
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index e82ff03bda02e..3ac3b4c054026 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -363,11 +363,13 @@ void bfqg_and_blkg_put(struct bfq_group *bfqg)
 
 void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq)
 {
-	struct bfq_group *bfqg = blkg_to_bfqg(rq->bio->bi_blkg);
+	struct blkcg_gq *blkg = bio_blkg_lookup(rq->bio);
+	struct bfq_group *bfqg;
 
-	if (!bfqg)
+	if (!blkg)
 		return;
 
+	bfqg = blkg_to_bfqg(blkg);
 	blkg_rwstat_add(&bfqg->stats.bytes, rq->cmd_flags, blk_rq_bytes(rq));
 	blkg_rwstat_add(&bfqg->stats.ios, rq->cmd_flags, 1);
 }
@@ -606,7 +608,7 @@ static void bfq_link_bfqg(struct bfq_data *bfqd, struct bfq_group *bfqg)
 
 struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
 {
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg_gq *blkg = bio_blkg_lookup(bio);
 	struct bfq_group *bfqg;
 
 	while (blkg) {
@@ -614,14 +616,16 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
 			blkg = blkg->parent;
 			continue;
 		}
+
 		bfqg = blkg_to_bfqg(blkg);
 		if (bfqg->pd.online) {
-			bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
+			bio_associate_blkcg_from_css(bio, &blkg->blkcg->css);
 			return bfqg;
 		}
 		blkg = blkg->parent;
 	}
-	bio_associate_blkg_from_css(bio,
+
+	bio_associate_blkcg_from_css(bio,
 				&bfqg_to_blkg(bfqd->root_group)->blkcg->css);
 	return bfqd->root_group;
 }
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0f75301b3115f..3d51d743552cb 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -128,6 +128,7 @@
 
 #include "elevator.h"
 #include "blk.h"
+#include "blk-cgroup.h"
 #include "blk-mq.h"
 #include "blk-mq-sched.h"
 #include "bfq-iosched.h"
@@ -2452,15 +2453,15 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
 	struct request *free = NULL;
 	bool ret;
 
+#ifdef CONFIG_BFQ_GROUP_IOSCHED
+	if (bic && bio_blkg_lookup(bio) == NULL)
+		return false;
+#endif
+
 	spin_lock_irq(&bfqd->lock);
 
 	if (bic) {
-		/*
-		 * Make sure cgroup info is uptodate for current process before
-		 * considering the merge.
-		 */
 		bfq_bic_update_cgroup(bic, bio);
-
 		bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf),
 					     bfq_actuator_index(bfqd, bio));
 	} else {
@@ -6245,6 +6246,13 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 	LIST_HEAD(free);
 
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
+	/*
+	 * Pin the blkg used to look up bfqg.  If this is the first IO for
+	 * the blkcg on this queue, create the bfqg before holding bfqd->lock.
+	 */
+	if (rq->bio && !bio_flagged(rq->bio, BIO_BLKG_REF))
+		bio_blkg(rq->bio);
+
 	if (!cgroup_subsys_on_dfl(io_cgrp_subsys) && rq->bio)
 		bfqg_stats_update_legacy_io(q, rq);
 #endif
diff --git a/block/bio.c b/block/bio.c
index 6a2f6fc3413e8..db33c993c2964 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -179,12 +179,7 @@ static inline gfp_t try_alloc_gfp(gfp_t gfp)
 
 void bio_uninit(struct bio *bio)
 {
-#ifdef CONFIG_BLK_CGROUP
-	if (bio->bi_blkg) {
-		blkg_put(bio->bi_blkg);
-		bio->bi_blkg = NULL;
-	}
-#endif
+	bio_clear_blkcg(bio);
 	if (bio_integrity(bio))
 		bio_integrity_free(bio);
 
@@ -233,10 +228,10 @@ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
 	bio->bi_end_io = NULL;
 	bio->bi_private = NULL;
 #ifdef CONFIG_BLK_CGROUP
-	bio->bi_blkg = NULL;
+	bio->bi_blkcg = NULL;
 	bio->issue_time_ns = 0;
 	if (bdev)
-		bio_associate_blkg(bio);
+		bio_associate_blkcg(bio);
 #ifdef CONFIG_BLK_CGROUP_IOCOST
 	bio->bi_iocost_cost = 0;
 #endif
@@ -281,7 +276,7 @@ void bio_reset(struct bio *bio, struct block_device *bdev, blk_opf_t opf)
 	bio->bi_io_vec = bv;
 	bio->bi_bdev = bdev;
 	if (bio->bi_bdev)
-		bio_associate_blkg(bio);
+		bio_associate_blkcg(bio);
 	bio->bi_opf = opf;
 }
 EXPORT_SYMBOL(bio_reset);
@@ -865,7 +860,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
 		if (bio->bi_bdev == bio_src->bi_bdev &&
 		    bio_flagged(bio_src, BIO_REMAPPED))
 			bio_set_flag(bio, BIO_REMAPPED);
-		bio_clone_blkg_association(bio, bio_src);
+		bio_clone_blkcg_association(bio, bio_src);
 	}
 
 	if (bio_crypt_clone(bio, bio_src, gfp) < 0)
@@ -1803,17 +1798,12 @@ void bio_endio(struct bio *bio)
 		goto again;
 	}
 
-#ifdef CONFIG_BLK_CGROUP
 	/*
 	 * Release cgroup info.  We shouldn't have to do this here, but quite
 	 * a few callers of bio_init fail to call bio_uninit, so we cover up
 	 * for that here at least for now.
 	 */
-	if (bio->bi_blkg) {
-		blkg_put(bio->bi_blkg);
-		bio->bi_blkg = NULL;
-	}
-#endif
+	bio_clear_blkcg(bio);
 
 	if (bio->bi_end_io)
 		bio->bi_end_io(bio);
diff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c
index 3ec21333f393b..7589c62099898 100644
--- a/block/blk-cgroup-fc-appid.c
+++ b/block/blk-cgroup-fc-appid.c
@@ -50,8 +50,14 @@ EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);
  */
 char *blkcg_get_fc_appid(struct bio *bio)
 {
-	if (!bio->bi_blkg || bio->bi_blkg->blkcg->fc_app_id[0] == '\0')
+	struct blkcg *blkcg = bio_blkcg(bio);
+
+	if (!blkcg)
+		return NULL;
+
+	if (blkcg->fc_app_id[0] == '\0')
 		return NULL;
-	return bio->bi_blkg->blkcg->fc_app_id;
+
+	return blkcg->fc_app_id;
 }
 EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d9676126c5b5d..a70f92f1541b1 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -170,10 +170,6 @@ static void __blkg_release(struct rcu_head *rcu)
 {
 	struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
 
-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
-	WARN_ON(!bio_list_empty(&blkg->async_bios));
-#endif
-
 	blkg_free(blkg);
 }
 
@@ -206,19 +202,18 @@ static void blkg_release(struct percpu_ref *ref)
 #ifdef CONFIG_BLK_CGROUP_PUNT_BIO
 static struct workqueue_struct *blkcg_punt_bio_wq;
 
-static void blkg_async_bio_workfn(struct work_struct *work)
+static void blkcg_async_bio_workfn(struct work_struct *work)
 {
-	struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
-					     async_bio_work);
+	struct blkcg *blkcg = container_of(work, struct blkcg, async_bio_work);
 	struct bio_list bios = BIO_EMPTY_LIST;
 	struct bio *bio;
 	struct blk_plug plug;
 	bool need_plug = false;
 
-	/* as long as there are pending bios, @blkg can't go away */
-	spin_lock(&blkg->async_bio_lock);
-	bio_list_merge_init(&bios, &blkg->async_bios);
-	spin_unlock(&blkg->async_bio_lock);
+	/* as long as there are pending bios, @blkcg can't go away */
+	spin_lock(&blkcg->async_bio_lock);
+	bio_list_merge_init(&bios, &blkcg->async_bios);
+	spin_unlock(&blkcg->async_bio_lock);
 
 	/* start plug only when bio_list contains at least 2 bios */
 	if (bios.head && bios.head->bi_next) {
@@ -239,15 +234,15 @@ static void blkg_async_bio_workfn(struct work_struct *work)
  */
 void blkcg_punt_bio_submit(struct bio *bio)
 {
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg *blkcg = bio_blkcg(bio);
 
-	if (blkg->parent) {
-		spin_lock(&blkg->async_bio_lock);
-		bio_list_add(&blkg->async_bios, bio);
-		spin_unlock(&blkg->async_bio_lock);
-		queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
+	if (blkcg && cgroup_parent(blkcg->css.cgroup)) {
+		spin_lock(&blkcg->async_bio_lock);
+		bio_list_add(&blkcg->async_bios, bio);
+		spin_unlock(&blkcg->async_bio_lock);
+		queue_work(blkcg_punt_bio_wq, &blkcg->async_bio_work);
 	} else {
-		/* never bounce for the root cgroup */
+		/* Never bounce if there is no non-root blkcg to queue on. */
 		submit_bio(bio);
 	}
 }
@@ -275,9 +270,9 @@ subsys_initcall(blkcg_punt_bio_init);
  */
 struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
 {
-	if (!bio || !bio->bi_blkg)
+	if (!bio || !bio_blkcg(bio))
 		return NULL;
-	return &bio->bi_blkg->blkcg->css;
+	return &bio_blkcg(bio)->css;
 }
 EXPORT_SYMBOL_GPL(bio_blkcg_css);
 
@@ -325,11 +320,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk,
 	INIT_LIST_HEAD(&blkg->q_node);
 	blkg->blkcg = blkcg;
 	blkg->iostat.blkg = blkg;
-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
-	spin_lock_init(&blkg->async_bio_lock);
-	bio_list_init(&blkg->async_bios);
-	INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
-#endif
 
 	u64_stats_init(&blkg->iostat.sync);
 	for_each_possible_cpu(cpu) {
@@ -1357,6 +1347,9 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)
 
 	mutex_unlock(&blkcg_pol_mutex);
 
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+	WARN_ON(!bio_list_empty(&blkcg->async_bios));
+#endif
 	free_percpu(blkcg->lhead);
 	kfree(blkcg);
 }
@@ -1406,6 +1399,11 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 	refcount_set(&blkcg->online_pin, 1);
 	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+	spin_lock_init(&blkcg->async_bio_lock);
+	bio_list_init(&blkcg->async_bios);
+	INIT_WORK(&blkcg->async_bio_work, blkcg_async_bio_workfn);
+#endif
 #ifdef CONFIG_CGROUP_WRITEBACK
 	INIT_LIST_HEAD(&blkcg->cgwb_list);
 #endif
@@ -2046,129 +2044,181 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
 	atomic64_add(delta, &blkg->delay_nsec);
 }
 
-static inline struct blkcg_gq *blkg_lookup_tryget(struct blkcg_gq *blkg)
+/*
+ * Return the blkg pinned by @bio through BIO_BLKG_REF.  The returned blkg is
+ * already owned by @bio and no extra reference is acquired.  If the pinned
+ * blkg can't be found, fall back to the root blkg.
+ */
+static struct blkcg_gq *bio_pinned_blkg(struct bio *bio)
 {
-retry:
-	if (blkg_tryget(blkg))
-		return blkg;
+	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+	struct blkcg_gq *blkg;
 
-	blkg = blkg->parent;
-	if (blkg)
-		goto retry;
+	rcu_read_lock();
+	blkg = blkg_lookup(bio_blkcg(bio), q);
+	rcu_read_unlock();
 
-	return NULL;
+	if (WARN_ON_ONCE(!blkg))
+		return q->root_blkg;
+	return blkg;
 }
+
 /**
- * blkg_tryget_closest - try and get a blkg ref on the closet blkg
+ * bio_blkg_lookup - look up a blkg associated with a bio
  * @bio: target bio
- * @css: target css
  *
- * As the failure mode here is to walk up the blkg tree, this ensure that the
- * blkg->parent pointers are always valid.  This returns the blkg that it ended
- * up taking a reference on or %NULL if no reference was taken.
+ * Look up the queue-local blkg for @bio's current device and blkcg without
+ * creating a missing blkg.  The first successful lookup pins the blkg to @bio;
+ * later lookups reuse the bio-owned reference.
  */
-static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
-		struct cgroup_subsys_state *css)
+struct blkcg_gq *bio_blkg_lookup(struct bio *bio)
 {
-	struct request_queue *q = bio->bi_bdev->bd_queue;
-	struct blkcg *blkcg = css_to_blkcg(css);
+	struct blkcg *blkcg = bio_blkcg(bio);
+	struct request_queue *q;
 	struct blkcg_gq *blkg;
 
+	if (bio_flagged(bio, BIO_BLKG_REF))
+		return bio_pinned_blkg(bio);
+
+	if (!blkcg || !bio->bi_bdev)
+		return NULL;
+
+	q = bdev_get_queue(bio->bi_bdev);
 	rcu_read_lock();
 	blkg = blkg_lookup(blkcg, q);
-	if (likely(blkg))
-		blkg = blkg_lookup_tryget(blkg);
+	if (blkg && blkg_tryget(blkg))
+		bio_set_flag(bio, BIO_BLKG_REF);
+	else
+		blkg = NULL;
 	rcu_read_unlock();
 
-	if (blkg)
-		return blkg;
+	return blkg;
+}
+EXPORT_SYMBOL_GPL(bio_blkg_lookup);
+
+/**
+ * bio_put_blkg_ref - drop the blkg reference pinned by a bio
+ * @bio: target bio
+ *
+ * Drop the bio-owned blkg reference acquired by bio_blkg(), if any.
+ */
+void bio_put_blkg_ref(struct bio *bio)
+{
+	if (bio_flagged(bio, BIO_BLKG_REF)) {
+		struct blkcg_gq *blkg = bio_pinned_blkg(bio);
+
+		blkg_put(blkg);
+		bio_clear_flag(bio, BIO_BLKG_REF);
+	}
+}
+EXPORT_SYMBOL_GPL(bio_put_blkg_ref);
+
+/**
+ * bio_blkg - look up the blkg associated with a bio
+ * @bio: target bio
+ *
+ * Look up the queue-local blkg for @bio's current device and blkcg.  If this
+ * is the first policy use of @bio, create the missing blkg hierarchy if
+ * necessary, pin the exact blkg, and mark @bio so bio_clear_blkcg() can drop
+ * the reference when the bio completes.
+ */
+struct blkcg_gq *bio_blkg(struct bio *bio)
+{
+	struct blkcg *blkcg = bio_blkcg(bio);
+	struct gendisk *disk;
+	struct request_queue *q;
+	struct blkcg_gq *blkg;
+
+	if (!blkcg || !bio->bi_bdev)
+		return NULL;
+
+	if (bio_flagged(bio, BIO_BLKG_REF))
+		return bio_pinned_blkg(bio);
+
+	disk = bio->bi_bdev->bd_disk;
+	q = disk->queue;
 
-	/*
-	 * Fast path failed, we're probably issuing IO in this cgroup the first
-	 * time, hold lock to create new blkg.
-	 */
 	spin_lock_irq(&q->queue_lock);
-	blkg = blkg_lookup_create(blkcg, bio->bi_bdev->bd_disk);
-	if (blkg)
-		blkg = blkg_lookup_tryget(blkg);
+	blkg = blkg_lookup_create(blkcg, disk);
+	if (blkg && blkg->blkcg == blkcg && blkg_tryget(blkg))
+		bio_set_flag(bio, BIO_BLKG_REF);
+	else
+		blkg = NULL;
 	spin_unlock_irq(&q->queue_lock);
 
 	return blkg;
 }
+EXPORT_SYMBOL_GPL(bio_blkg);
 
 /**
- * bio_associate_blkg_from_css - associate a bio with a specified css
+ * bio_associate_blkcg_from_css - associate a bio with a specified css
  * @bio: target bio
  * @css: target css
  *
- * Associate @bio with the blkg found by combining the css's blkg and the
- * request_queue of the @bio.  An association failure is handled by walking up
- * the blkg tree.  Therefore, the blkg associated can be anything between @blkg
- * and q->root_blkg.  This situation only happens when a cgroup is dying and
- * then the remaining bios will spill to the closest alive blkg.
+ * Associate @bio with the blkcg found from @css.  The queue-local blkg is
+ * created and pinned by bio_blkg() when blkcg policies need it.
  *
- * A reference will be taken on the blkg and will be released when @bio is
+ * A reference will be taken on the blkcg and will be released when @bio is
  * freed.
  */
-void bio_associate_blkg_from_css(struct bio *bio,
+void bio_associate_blkcg_from_css(struct bio *bio,
 				 struct cgroup_subsys_state *css)
 {
-	if (bio->bi_blkg)
-		blkg_put(bio->bi_blkg);
+	struct blkcg *blkcg;
 
-	if (css && css->parent) {
-		bio->bi_blkg = blkg_tryget_closest(bio, css);
-	} else {
-		blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg);
-		bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg;
-	}
+	if (!css || !css->parent)
+		css = &blkcg_root.css;
+
+	blkcg = css_to_blkcg(css);
+	if (bio_blkcg(bio) == blkcg)
+		return;
+
+	css_get(css);
+	bio_clear_blkcg(bio);
+	bio->bi_blkcg = blkcg;
 }
-EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
+EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css);
 
 /**
- * bio_associate_blkg - associate a bio with a blkg
+ * bio_associate_blkcg - associate a bio with a blkcg
  * @bio: target bio
  *
- * Associate @bio with the blkg found from the bio's css and request_queue.
- * If one is not found, bio_lookup_blkg() creates the blkg.  If a blkg is
- * already associated, the css is reused and association redone as the
- * request_queue may have changed.
+ * Associate @bio with the blkcg found from the bio's css.  If a blkcg is
+ * already associated, keep it as blkcg association is not queue-local.
  */
-void bio_associate_blkg(struct bio *bio)
+void bio_associate_blkcg(struct bio *bio)
 {
 	struct cgroup_subsys_state *css;
 
 	if (blk_op_is_passthrough(bio->bi_opf))
 		return;
 
-	if (bio->bi_blkg) {
-		css = bio_blkcg_css(bio);
-		bio_associate_blkg_from_css(bio, css);
-	} else {
-		rcu_read_lock();
-		css = blkcg_css();
-		if (!css_tryget_online(css))
-			css = NULL;
-		rcu_read_unlock();
+	if (bio_blkcg(bio))
+		return;
 
-		bio_associate_blkg_from_css(bio, css);
-		if (css)
-			css_put(css);
-	}
+	rcu_read_lock();
+	css = blkcg_css();
+	if (!css_tryget_online(css))
+		css = NULL;
+	rcu_read_unlock();
+
+	bio_associate_blkcg_from_css(bio, css);
+	if (css)
+		css_put(css);
 }
-EXPORT_SYMBOL_GPL(bio_associate_blkg);
+EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
- * bio_clone_blkg_association - clone blkg association from src to dst bio
+ * bio_clone_blkcg_association - clone blkcg association from src to dst bio
  * @dst: destination bio
  * @src: source bio
  */
-void bio_clone_blkg_association(struct bio *dst, struct bio *src)
+void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
 {
-	if (src->bi_blkg)
-		bio_associate_blkg_from_css(dst, bio_blkcg_css(src));
+	if (bio_blkcg(src))
+		bio_associate_blkcg_from_css(dst, bio_blkcg_css(src));
 }
-EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
+EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);
 
 static int blk_cgroup_io_type(struct bio *bio)
 {
@@ -2181,20 +2231,27 @@ static int blk_cgroup_io_type(struct bio *bio)
 
 void blk_cgroup_bio_start(struct bio *bio)
 {
-	struct blkcg *blkcg = bio->bi_blkg->blkcg;
+	struct blkcg *blkcg = bio_blkcg(bio);
+	struct blkcg_gq *blkg;
 	int rwd = blk_cgroup_io_type(bio), cpu;
 	struct blkg_iostat_set *bis;
 	unsigned long flags;
 
 	if (!cgroup_subsys_on_dfl(io_cgrp_subsys))
 		return;
+	if (!blkcg)
+		return;
 
 	/* Root-level stats are sourced from system-wide IO stats */
 	if (!cgroup_parent(blkcg->css.cgroup))
 		return;
 
+	blkg = bio_blkg_lookup(bio);
+	if (!blkg)
+		return;
+
 	cpu = get_cpu();
-	bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
+	bis = per_cpu_ptr(blkg->iostat_cpu, cpu);
 	flags = u64_stats_update_begin_irqsave(&bis->sync);
 
 	/*
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 615390f751aa2..b457c2b4ac7c8 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -73,14 +73,7 @@ struct blkcg_gq {
 	struct blkg_iostat_set		iostat;
 
 	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
-#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
-	spinlock_t			async_bio_lock;
-	struct bio_list			async_bios;
-#endif
-	union {
-		struct work_struct	async_bio_work;
-		struct work_struct	free_work;
-	};
+	struct work_struct		free_work;
 
 	atomic_t			use_delay;
 	atomic64_t			delay_nsec;
@@ -111,6 +104,11 @@ struct blkcg {
 	 */
 	struct llist_head __percpu	*lhead;
 
+#ifdef CONFIG_BLK_CGROUP_PUNT_BIO
+	spinlock_t			async_bio_lock;
+	struct bio_list			async_bios;
+	struct work_struct		async_bio_work;
+#endif
 #ifdef CONFIG_BLK_CGROUP_FC_APPID
 	char                            fc_app_id[FC_APPID_LEN];
 #endif
@@ -124,6 +122,11 @@ static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 	return css ? container_of(css, struct blkcg, css) : NULL;
 }
 
+static inline struct blkcg *bio_blkcg(struct bio *bio)
+{
+	return bio->bi_blkcg;
+}
+
 /*
  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
  * request_queue (q).  This is used by blkcg policies which need to track
@@ -276,6 +279,9 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
 	return blkg;
 }
 
+struct blkcg_gq *bio_blkg_lookup(struct bio *bio);
+struct blkcg_gq *bio_blkg(struct bio *bio);
+
 /**
  * blkg_to_pd - get policy private data
  * @blkg: blkg of interest
@@ -343,6 +349,18 @@ static inline void blkg_put(struct blkcg_gq *blkg)
 	percpu_ref_put(&blkg->refcnt);
 }
 
+static inline void bio_clear_blkcg(struct bio *bio)
+{
+	struct blkcg *blkcg = bio_blkcg(bio);
+
+	bio_put_blkg_ref(bio);
+
+	if (blkcg) {
+		css_put(&blkcg->css);
+		bio->bi_blkcg = NULL;
+	}
+}
+
 /**
  * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
  * @d_blkg: loop cursor pointing to the current descendant
@@ -455,7 +473,7 @@ static inline void blkcg_clear_delay(struct blkcg_gq *blkg)
  */
 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio)
 {
-	return rq->bio->bi_blkg == bio->bi_blkg &&
+	return bio_blkcg(rq->bio) == bio_blkcg(bio) &&
 		bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio);
 }
 
@@ -481,6 +499,9 @@ struct blkcg_policy {
 struct blkcg {
 };
 
+static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
+static inline struct blkcg_gq *bio_blkg_lookup(struct bio *bio) { return NULL; }
+static inline struct blkcg_gq *bio_blkg(struct bio *bio) { return NULL; }
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 static inline void blkg_init_queue(struct request_queue *q) { }
 static inline int blkcg_init_disk(struct gendisk *disk) { return 0; }
@@ -497,6 +518,7 @@ static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
 static inline void blkg_get(struct blkcg_gq *blkg) { }
 static inline void blkg_put(struct blkcg_gq *blkg) { }
+static inline void bio_clear_blkcg(struct bio *bio) { }
 static inline void blk_cgroup_bio_start(struct bio *bio) { }
 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }
 
diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
index 2a5c52ab74b4c..5ef4baab444bb 100644
--- a/block/blk-crypto-fallback.c
+++ b/block/blk-crypto-fallback.c
@@ -187,7 +187,7 @@ static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,
 	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_write_stream	= bio_src->bi_write_stream;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
-	bio_clone_blkg_association(bio, bio_src);
+	bio_clone_blkcg_association(bio, bio_src);
 
 	/*
 	 * Move page array up in the allocated memory for the bio vecs as far as
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 8b2aeba2e1e39..62ffd759bb954 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2686,7 +2686,7 @@ iocg_handle_over_budget(struct rq_qos *rqos, struct ioc_gq *iocg,
 
 static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
 {
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg_gq *blkg = bio_blkg(bio);
 	struct ioc *ioc = rqos_to_ioc(rqos);
 	struct ioc_gq *iocg = blkg_to_iocg(blkg);
 	struct ioc_now now;
@@ -2775,7 +2775,7 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
 static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
 			   struct bio *bio)
 {
-	struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
+	struct ioc_gq *iocg = blkg_to_iocg(bio_blkg_lookup(bio));
 	struct ioc *ioc = rqos_to_ioc(rqos);
 	sector_t bio_end = bio_end_sector(bio);
 	struct ioc_now now;
@@ -2833,9 +2833,13 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
 
 static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
 {
-	struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
+	struct ioc_gq *iocg;
+
+	if (!bio->bi_iocost_cost)
+		return;
 
-	if (iocg && bio->bi_iocost_cost)
+	iocg = blkg_to_iocg(bio_blkg_lookup(bio));
+	if (iocg)
 		atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime);
 }
 
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index cef02b6c5fa91..7ad18a538d7e2 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -463,7 +463,7 @@ static void check_scale_change(struct iolatency_grp *iolat)
 static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
 {
 	struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg_gq *blkg = bio_blkg(bio);
 	bool issue_as_root = bio_issue_as_root_blkg(bio);
 
 	if (!blkiolat->enabled)
@@ -590,11 +590,14 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
 	bool issue_as_root = bio_issue_as_root_blkg(bio);
 	int inflight = 0;
 
-	blkg = bio->bi_blkg;
-	if (!blkg || !bio_flagged(bio, BIO_QOS_THROTTLED))
+	if (!bio_flagged(bio, BIO_QOS_THROTTLED))
 		return;
 
-	iolat = blkg_to_lat(bio->bi_blkg);
+	blkg = bio_blkg_lookup(bio);
+	if (!blkg)
+		return;
+
+	iolat = blkg_to_lat(blkg);
 	if (!iolat)
 		return;
 
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index 8fa8bca350629..5e3f8e49550da 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -132,7 +132,7 @@ static struct blkcg_policy ioprio_policy = {
 
 void blkcg_set_ioprio(struct bio *bio)
 {
-	struct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio->bi_blkg->blkcg);
+	struct ioprio_blkcg *blkcg = blkcg_to_ioprio_blkcg(bio_blkcg(bio));
 	u16 prio;
 
 	if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index ffc3b70065d4b..3828c38579002 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1792,7 +1792,7 @@ static bool tg_within_limit(struct throtl_grp *tg, struct bio *bio, bool rw)
 bool __blk_throtl_bio(struct bio *bio)
 {
 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
-	struct blkcg_gq *blkg = bio->bi_blkg;
+	struct blkcg_gq *blkg = bio_blkg(bio);
 	struct throtl_qnode *qn = NULL;
 	struct throtl_grp *tg = blkg_to_tg(blkg);
 	struct throtl_service_queue *sq;
diff --git a/block/blk-throttle.h b/block/blk-throttle.h
index 9d7a42c039a15..609a126c7ccb2 100644
--- a/block/blk-throttle.h
+++ b/block/blk-throttle.h
@@ -173,7 +173,7 @@ static inline bool blk_should_throtl(struct bio *bio)
 	if (!blk_throtl_activated(bio->bi_bdev->bd_queue))
 		return false;
 
-	tg = blkg_to_tg(bio->bi_blkg);
+	tg = blkg_to_tg(bio_blkg(bio));
 	if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
 		if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
 			bio_set_flag(bio, BIO_CGROUP_ACCT);
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 3fa3b13a410f4..c0f945b8d9413 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -848,7 +848,7 @@ static CLOSURE_CALLBACK(cached_dev_read_done)
 		s->iop.bio->bi_iter.bi_sector =
 			s->cache_miss->bi_iter.bi_sector;
 		s->iop.bio->bi_iter.bi_size = s->insert_bio_sectors << 9;
-		bio_clone_blkg_association(s->iop.bio, s->cache_miss);
+		bio_clone_blkcg_association(s->iop.bio, s->cache_miss);
 		bch_bio_map(s->iop.bio, NULL);
 
 		bio_copy_data(s->cache_miss, s->iop.bio);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index d413bfaf35278..cd68eec77f5a1 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1373,7 +1373,7 @@ void dm_submit_bio_remap(struct bio *clone, struct bio *tgt_clone)
 	if (!tgt_clone)
 		tgt_clone = clone;
 
-	bio_clone_blkg_association(tgt_clone, io->orig_bio);
+	bio_clone_blkcg_association(tgt_clone, io->orig_bio);
 
 	/*
 	 * Account io->origin_bio to DM dev on behalf of target
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d1465bcd86c81..af55f8efa46bc 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9355,7 +9355,7 @@ void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
 		return;
 
 	bio_chain(discard_bio, bio);
-	bio_clone_blkg_association(discard_bio, bio);
+	bio_clone_blkcg_association(discard_bio, bio);
 	mddev_trace_remap(mddev, discard_bio, bio->bi_iter.bi_sector);
 	submit_bio_noacct(discard_bio);
 }
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
index 4176046627beb..54e4adb0ccb7d 100644
--- a/drivers/nvdimm/nd_virtio.c
+++ b/drivers/nvdimm/nd_virtio.c
@@ -121,7 +121,7 @@ int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
 
 		if (!child)
 			return -ENOMEM;
-		bio_clone_blkg_association(child, bio);
+		bio_clone_blkcg_association(child, bio);
 		child->bi_iter.bi_sector = -1;
 		bio_chain(child, bio);
 		submit_bio(child);
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 6dabe73ad790d..6512dbd9516fc 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -484,7 +484,7 @@ static struct bio *gfs2_chain_bio(struct bio *prev, unsigned int nr_iovecs,
 	struct bio *new;
 
 	new = bio_alloc(prev->bi_bdev, nr_iovecs, opf, GFP_NOIO);
-	bio_clone_blkg_association(new, prev);
+	bio_clone_blkcg_association(new, prev);
 	new->bi_iter.bi_sector = sector;
 	bio_chain(new, prev);
 	submit_bio(prev);
@@ -1114,4 +1114,3 @@ const struct gfs2_log_operations *gfs2_log_ops[] = {
 	&gfs2_revoke_lops,
 	NULL,
 };
-
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 8f33f717b14f5..e5799fdf431d2 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -503,18 +503,20 @@ static inline void bio_release_pages(struct bio *bio, bool mark_dirty)
 	disk_devt((bio)->bi_bdev->bd_disk)
 
 #ifdef CONFIG_BLK_CGROUP
-void bio_associate_blkg(struct bio *bio);
-void bio_associate_blkg_from_css(struct bio *bio,
+void bio_associate_blkcg(struct bio *bio);
+void bio_associate_blkcg_from_css(struct bio *bio,
 				 struct cgroup_subsys_state *css);
-void bio_clone_blkg_association(struct bio *dst, struct bio *src);
+void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
+void bio_put_blkg_ref(struct bio *bio);
 void blkcg_punt_bio_submit(struct bio *bio);
 #else	/* CONFIG_BLK_CGROUP */
-static inline void bio_associate_blkg(struct bio *bio) { }
-static inline void bio_associate_blkg_from_css(struct bio *bio,
+static inline void bio_associate_blkcg(struct bio *bio) { }
+static inline void bio_associate_blkcg_from_css(struct bio *bio,
 					       struct cgroup_subsys_state *css)
 { }
-static inline void bio_clone_blkg_association(struct bio *dst,
+static inline void bio_clone_blkcg_association(struct bio *dst,
 					      struct bio *src) { }
+static inline void bio_put_blkg_ref(struct bio *bio) { }
 static inline void blkcg_punt_bio_submit(struct bio *bio)
 {
 	submit_bio(bio);
@@ -524,10 +526,12 @@ static inline void blkcg_punt_bio_submit(struct bio *bio)
 static inline void bio_set_dev(struct bio *bio, struct block_device *bdev)
 {
 	bio_clear_flag(bio, BIO_REMAPPED);
-	if (bio->bi_bdev != bdev)
+	if (bio->bi_bdev != bdev) {
+		bio_put_blkg_ref(bio);
 		bio_clear_flag(bio, BIO_BPS_THROTTLED);
+	}
 	bio->bi_bdev = bdev;
-	bio_associate_blkg(bio);
+	bio_associate_blkcg(bio);
 }
 
 /*
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 8808ee76e73c0..5f95c2e0e90b0 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -246,12 +246,10 @@ struct bio {
 	void			*bi_private;
 #ifdef CONFIG_BLK_CGROUP
 	/*
-	 * Represents the association of the css and request_queue for the bio.
-	 * If a bio goes direct to device, it will not have a blkg as it will
-	 * not have a request_queue associated with it.  The reference is put
-	 * on release of the bio.
+	 * Represents the blkcg css association for the bio.  The reference is
+	 * put on release of the bio.
 	 */
-	struct blkcg_gq		*bi_blkg;
+	struct blkcg		*bi_blkcg;
 	/* Time that this bio was issued. */
 	u64			issue_time_ns;
 #ifdef CONFIG_BLK_CGROUP_IOCOST
@@ -309,6 +307,7 @@ enum {
 	BIO_TRACE_COMPLETION,	/* bio_endio() should trace the final completion
 				 * of this bio. */
 	BIO_CGROUP_ACCT,	/* has been accounted to a cgroup */
+	BIO_BLKG_REF,		/* bio pins the associated blkg */
 	BIO_QOS_THROTTLED,	/* bio went through rq_qos throttle path */
 	/*
 	 * This bio has completed bps throttling at the single tg granularity,
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 62552a2ce5b9e..4f869fe9cc90f 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -262,7 +262,7 @@ static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
 	 * regular writeback instead of writing things out itself.
 	 */
 	if (wbc->wb)
-		bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css);
+		bio_associate_blkcg_from_css(bio, wbc->wb->blkcg_css);
 }
 
 void inode_switch_wbs_work_fn(struct work_struct *work);
diff --git a/mm/page_io.c b/mm/page_io.c
index b23f494fcc83d..112e504756055 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -316,7 +316,7 @@ static inline void count_swpout_vm_event(struct folio *folio)
 }
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
-static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
+static void bio_associate_blkcg_from_page(struct bio *bio, struct folio *folio)
 {
 	struct cgroup_subsys_state *css;
 	struct mem_cgroup *memcg;
@@ -331,12 +331,12 @@ static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
 		css = NULL;
 	rcu_read_unlock();
 
-	bio_associate_blkg_from_css(bio, css);
+	bio_associate_blkcg_from_css(bio, css);
 	if (css)
 		css_put(css);
 }
 #else
-#define bio_associate_blkg_from_page(bio, folio)		do { } while (0)
+#define bio_associate_blkcg_from_page(bio, folio)	do { } while (0)
 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
 
 struct swap_iocb {
@@ -436,7 +436,7 @@ static void swap_writepage_bdev_sync(struct folio *folio,
 	bio.bi_iter.bi_sector = swap_folio_sector(folio);
 	bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
 
-	bio_associate_blkg_from_page(&bio, folio);
+	bio_associate_blkcg_from_page(&bio, folio);
 	count_swpout_vm_event(folio);
 
 	folio_start_writeback(folio);
@@ -456,7 +456,7 @@ static void swap_writepage_bdev_async(struct folio *folio,
 	bio->bi_end_io = end_swap_bio_write;
 	bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 
-	bio_associate_blkg_from_page(bio, folio);
+	bio_associate_blkcg_from_page(bio, folio);
 	count_swpout_vm_event(folio);
 	folio_start_writeback(folio);
 	folio_unlock(folio);

3/2

2026/08/04 07:16

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 16348
							output: 21
							thoughts: 478

Thoughts:

**Analyzing a Core Block Layer Change for Block Cgroup Association**

Okay, so I'm looking at a patch that fundamentally alters how `bio` structures relate to `blkcg` (block cgroups). They're replacing `bio->bi_blkg` with `bio->bi_blkcg`, and introducing new functions, `bio_blkg_lookup()` and `bio_blkg()`. This is a pretty significant change, really digging into the core of how block I/O interacts with cgroups.

The sheer number of files touched is a dead giveaway: `block/bfq-cgroup.c`, `block/bfq-iosched.c`, `block/bio.c`, `block/blk-cgroup-fc-appid.c`, `block/blk-cgroup.c`, and so on, all the way through to `mm/page_io.c`, plus header files like `include/linux/bio.h`. It really touches a broad swath of the block layer. This isn't just a cosmetic tweak; it's a deep dive into the functional logic of how we look up and pin the `blkg` structure associated with a `bio`. That's critical, especially for things like I/O scheduling and throttling.

This is going to impact virtualized environments, too. I'll need to pay close attention to the implications there.

Now, let's figure out what configuration options are needed for this. I'm guessing `CONFIG_BLK_CGROUP` is a given; it's right in the name of the change. `CONFIG_BFQ_GROUP_IOSCHED` is mentioned in the BFQ scheduler, so that's probably related. Then there's `CONFIG_BLK_CGROUP_PUNT_BIO`, `CONFIG_BLK_CGROUP_IOCOST`, and `CONFIG_BLK_CGROUP_IOLATENCY`. I should probably use `grepper` to be sure I haven't missed anything, and make sure I know the exact config names.

4/2

2026/08/04 07:16

tool

grepper

Args:

{
  "Expression": "config BLK_CGROUP"
}

Results:

{
  "Output": "block/Kconfig=39=config BLK_RQ_ALLOC_TIME\n--\nblock/Kconfig-41-\nblock/Kconfig:42:config BLK_CGROUP_RWSTAT\nblock/Kconfig-43-\tbool\nblock/Kconfig-44-\nblock/Kconfig:45:config BLK_CGROUP_PUNT_BIO\nblock/Kconfig-46-\tbool\n--\nblock/Kconfig=127=config BLK_WBT_MQ\n--\nblock/Kconfig-133-\nblock/Kconfig:134:config BLK_CGROUP_IOLATENCY\nblock/Kconfig-135-\tbool \"Enable support for latency based cgroup IO protection\"\n--\nblock/Kconfig-144-\nblock/Kconfig:145:config BLK_CGROUP_FC_APPID\nblock/Kconfig-146-\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n--\nblock/Kconfig-153-\nblock/Kconfig:154:config BLK_CGROUP_IOCOST\nblock/Kconfig-155-\tbool \"Enable support for cost model based cgroup IO controller\"\n--\nblock/Kconfig-163-\nblock/Kconfig:164:config BLK_CGROUP_IOPRIO\nblock/Kconfig-165-\tbool \"Cgroup I/O controller for assigning an I/O priority class\"\n--\ninit/Kconfig=1099=config MEMCG_V1\n--\ninit/Kconfig-1115-\ninit/Kconfig:1116:config BLK_CGROUP\ninit/Kconfig-1117-\tbool \"IO controller\"\n"
}

5/2

2026/08/04 07:16

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 17720
							output: 23
							thoughts: 12

Thoughts:

Okay, here's my attempt at summarizing that thought process, tailored for an expert audience:

**BFQ Configuration Name Hunt**

Alright, time to get laser-focused. I need to pinpoint the *exact* configuration names associated with BFQ. No ambiguity here – I'm looking for the precise identifiers, the variables, the options, whatever the system uses to *internally* define and manage BFQ's behavior. I can't afford to be vague or use generic terminology; I need the nitty-gritty details. Are we talking kernel parameters? Module options? Configuration files? I'm going to dig until I find the definitive source that clearly lays out the naming conventions. It's time to sift through documentation, source code, and perhaps even some debugging output to make absolutely sure I have the accurate config names.

6/2

2026/08/04 07:16

tool

grepper

Args:

{
  "Expression": "config BFQ_GROUP_IOSCHED"
}

Results:

{
  "Output": "block/Kconfig.iosched=19=config IOSCHED_BFQ\n--\nblock/Kconfig.iosched-29-\nblock/Kconfig.iosched:30:config BFQ_GROUP_IOSCHED\nblock/Kconfig.iosched-31-       bool \"BFQ hierarchical scheduling support\"\n"
}

7/2

2026/08/04 07:16

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 18016
							output: 25
							thoughts: 266

Thoughts:

**Analyzing Block I/O Cgroup Functionality**

Alright, let's dive into this block I/O cgroup implementation. First, I need to keep the relevant configuration options in mind: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, and `BFQ_GROUP_IOSCHED`. These are the flags defining what's enabled.

Now, let's list out the core functions that manage the cgroup association and lifecycle of block I/O operations. I'm focusing on these: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, and `bio_clear_blkcg`. These should be the heart of the interaction.

Okay, next I quickly check which of these functions are actually exposed. And the answer is "All of them!". Excellent. That means this is a relatively self-contained, well-defined set of building blocks. Good to know.

Time to head into `block/blk-cgroup.c` and dig into the implementation details of each. This is where the real work happens. Let's see how these pieces fit together.

8/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "EXPORT_SYMBOL_GPL\\(bio_blkg"
}

Results:

{
  "Output": "block/blk-cgroup.c=2074=struct blkcg_gq *bio_blkg_lookup(struct bio *bio)\n--\nblock/blk-cgroup.c-2096-}\nblock/blk-cgroup.c:2097:EXPORT_SYMBOL_GPL(bio_blkg_lookup);\nblock/blk-cgroup.c-2098-\n--\nblock/blk-cgroup.c=2125=struct blkcg_gq *bio_blkg(struct bio *bio)\n--\nblock/blk-cgroup.c-2150-}\nblock/blk-cgroup.c:2151:EXPORT_SYMBOL_GPL(bio_blkg);\nblock/blk-cgroup.c-2152-\n"
}

9/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 18825
							output: 27
							thoughts: 23

Thoughts:

Okay, here's my take on those thoughts, tailored for an expert audience:

**Analyzing `bio_associate_blkcg` and `bio_clone_blkcg_association`**

Alright, time to dig into `bio_associate_blkcg` and `bio_clone_blkcg_association`. These are key for block device CGroups, so let's make sure our understanding is rock solid. I need to be completely clear on the responsibilities of each of these functions. From what I recall, `bio_associate_blkcg` is the primary entry point for, well, associating a bio (Block IO request) with a specific blkcg (Block CGroup). I need to re-examine the mechanics of how it handles the association: Is it a direct assignment, or does it involve some sort of internal tracking or metadata update? I need to clarify the interaction between the bio's context and the target blkcg.

`bio_clone_blkcg_association`... now, that one's interesting. The name suggests this handles cloning the blkcg association when a bio is duplicated or split, perhaps. Is it a deep copy or shallow copy? I want to pay attention to how they handle the propagation of the blkcg association through bio cloning. It seems critical for preserving resource accounting across complex bio operations, which may require special consideration when it comes to nested or shared CGroups.

I should also make sure to check the locking around these functions, especially if they are called in interrupt context or from multiple threads. Concurrency issues around blkcg association could lead to performance problems or, worse, data corruption. Let's make sure the details of synchronization are sound.

10/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "EXPORT_SYMBOL_GPL\\(bio_associate_blkcg"
}

Results:

{
  "Output": "block/blk-cgroup.c=2164=void bio_associate_blkcg_from_css(struct bio *bio,\n--\nblock/blk-cgroup.c-2179-}\nblock/blk-cgroup.c:2180:EXPORT_SYMBOL_GPL(bio_associate_blkcg_from_css);\nblock/blk-cgroup.c-2181-\n--\nblock/blk-cgroup.c=2189=void bio_associate_blkcg(struct bio *bio)\n--\nblock/blk-cgroup.c-2208-}\nblock/blk-cgroup.c:2209:EXPORT_SYMBOL_GPL(bio_associate_blkcg);\nblock/blk-cgroup.c-2210-\n"
}

11/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 19430
							output: 29
							thoughts: 11

Thoughts:

Okay, here's my interpretation of that thought process, assuming I'm an expert in this field, presented as a first-person summary:

**The Crucial `bio_clone_blkcg_association` Consideration**

Alright, so the core of my thinking here centers around this function, `bio_clone_blkcg_association`. I immediately understand the implication – we're dealing with cloning, likely a `bio` structure, and it's intimately tied to block I/O and control groups (blkcg). My brain instantly starts running through the scenarios: what's the context? Is this about a copy-on-write operation, a remapping, or something else entirely?

The fact that we're talking about cloning suggests that we need to be careful about resource attribution and tracking. Specifically, how do we correctly propagate the blkcg association across the cloned `bio`? Are we creating a completely new association or maintaining the existing one? If it's the latter, we have to consider the potential pitfalls of shared resources and race conditions. If it is the former, what is the right way to determine that information? Are there implications for the I/O scheduler and accounting?

My expertise kicks in here, reminding me to consider potential memory management issues and synchronization needs. We need to be wary of making the blkcg association part of the `bio` itself. That could be problematic. I need to dive into the specific code and the surrounding context. It is important to know if the `blkcg` association is going to be used by the scheduler. And if so, should the scheduler treat this as a new I/O with different weights? What is the impact of accounting? This function is right at the heart of how we manage resources and isolation within the block I/O stack and I know it's a critical point for performance and correctness. Any errors here could lead to cascading problems down the line. I must scrutinize this carefully.

12/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "EXPORT_SYMBOL_GPL\\(bio_clone_blkcg_association"
}

Results:

{
  "Output": "block/blk-cgroup.c=2216=void bio_clone_blkcg_association(struct bio *dst, struct bio *src)\n--\nblock/blk-cgroup.c-2220-}\nblock/blk-cgroup.c:2221:EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);\nblock/blk-cgroup.c-2222-\n"
}

13/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 19988
							output: 29
							thoughts: 11

Thoughts:

Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:

**Working with `bio_put_blkg_ref`**

Right, so I see we're dealing with `bio_put_blkg_ref`. Immediately, my mind jumps to the implications for block device interactions within the BIOS environment. This suggests a low-level, critical function, likely involved in managing block references, and potentially handling the intricacies of memory allocation and deallocation specifically within the context of the BIOS. I'm imagining it's the core of how we manipulate persistent storage at the most fundamental level. We're probably talking about handling different types of block device types, such as disk drives, solid-state drives, or perhaps even virtual block devices.

Given the naming convention, I’m guessing this isn’t a simple wrapper. It feels like a key piece to managing data structures related to block references. I need to understand the underlying data structures it operates on. What data types are involved? Are we dealing with lists, trees, or perhaps something more specialized for managing block maps or extents? The interaction with the underlying hardware, and how these references are translated into physical disk addresses, will be critical.

Furthermore, I have to consider the potential for race conditions. If it’s not thread-safe, or if locking isn't handled correctly, we could easily corrupt data. I need to know how it interfaces with any other concurrent operations or interrupt handlers within the BIOS. Error handling is paramount, too. How robust is the error handling? What kind of checks are in place to prevent data loss or system instability if something goes wrong? Are there any retry mechanisms? This likely plays a crucial role in our boot process stability.

Finally, I’m thinking about performance. Is this function optimized for speed? Are there any potential bottlenecks, especially with large block sizes or frequent write operations? And how does it relate to the `bio_` framework? It's likely a critical component of block I/O operations and I need to consider it's implications in that context.

14/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "EXPORT_SYMBOL_GPL\\(bio_put_blkg_ref"
}

Results:

{
  "Output": "block/blk-cgroup.c=2105=void bio_put_blkg_ref(struct bio *bio)\n--\nblock/blk-cgroup.c-2113-}\nblock/blk-cgroup.c:2114:EXPORT_SYMBOL_GPL(bio_put_blkg_ref);\nblock/blk-cgroup.c-2115-\n"
}

15/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 20573
							output: 29
							thoughts: 128

Thoughts:

**Adding New Block IO CGroups Functions**

Okay, so I've been working on these new Block IO CGroups functions, and I need to make sure they're properly documented and integrated. I'm going to add them to the `FocusSymbols` list so they're easily tracked and considered for future work. That means including: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and then making sure the updated `blkcg_punt_bio_submit` function is included too.

Wait a second, `blkcg_punt_bio_submit` was already present. I need to double-check that this function is properly exported. I need to make sure there are no issues with it being changed. I will check for this.

16/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "EXPORT_SYMBOL_GPL\\(blkcg_punt_bio_submit"
}

Results:

{
  "Output": "block/blk-cgroup.c=235=void blkcg_punt_bio_submit(struct bio *bio)\n--\nblock/blk-cgroup.c-248-}\nblock/blk-cgroup.c:249:EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit);\nblock/blk-cgroup.c-250-\n"
}

17/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 21031
							output: 26
							thoughts: 664

Thoughts:

**Analyzing Block Layer CGROUP API Changes**

Okay, so I'm looking at these changes and the first thing that jumps out is that it *is* an API change. My first thought is to dig into the implementation, and I need to be careful about not documenting static inline functions, like `bio_clear_blkcg` which is defined in `block/blk-cgroup.h`, or static functions, like `bio_pinned_blkg`, found in `block/blk-cgroup.c`. I have to remember this when I am documenting them.

I need to make sure I don't miss anything, so let me do a quick scan of other functions involved. Let's see... there's `bfq_bio_bfqg`, `bfq_bio_merge`, `bfq_insert_request`, some `bio` manipulation functions in `block/bio.c` (`bio_uninit`, `bio_init`, `bio_reset`, `__bio_clone`, `bio_endio`), and a few others that I need to keep in mind, like the ones in the cgroup specific files like `blkcg_get_fc_appid`, `blk_cgroup_bio_start`, `blk_crypto_alloc_enc_bio`, `ioc_rqos_throttle`, `ioc_rqos_merge`, `ioc_rqos_done_bio`, `blkcg_iolatency_throttle`, `blkcg_iolatency_done_bio`, `blkcg_set_ioprio`, and `__blk_throtl_bio`.

The key change here, though, seems to be a new set of API functions. Let's focus on these new additions: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, and `bio_put_blkg_ref`. Those seem to be the critical ones that make the core API change.

I'll need to go back and investigate the configuration options that are affected by this. I need to make sure to document that: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `BLK_CGROUP_FC_APPID`, and `BLK_CGROUP_PUNT_BIO` are all affected.

Right now, I should focus on `bio_blkg_lookup` and `bio_blkg`, as those seem to be the critical changes in this new API. I will need to verify the usage of `BLK_CGROUP_PUNT_BIO` and how that affects the block layer as well, so I'll need to go and look into that in Kconfig.

18/2

2026/08/04 07:17

tool

grepper

Args:

{
  "Expression": "config BLK_CGROUP_PUNT_BIO"
}

Results:

{
  "Output": "block/Kconfig=42=config BLK_CGROUP_RWSTAT\n--\nblock/Kconfig-44-\nblock/Kconfig:45:config BLK_CGROUP_PUNT_BIO\nblock/Kconfig-46-\tbool\n"
}

19/2

2026/08/04 07:17

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 22428
							output: 26
							thoughts: 33

Thoughts:

Okay, here's my interpretation of those thoughts, tailored for an expert audience, and delivered as a first-person summary:

**Digging into a Mysterious Boolean**

Right, so this flag, this boolean, it's not exposed directly. It's *hidden*. That immediately tells me it's being toggled by something else within the system. We can't simply flip the switch ourselves, we have to understand the *why* and the *how* of its activation. So, my next step is clear: I need to trace back through the code, or examine the configuration, whatever relevant mechanisms are present, to figure out what's actually *selecting* this hidden bool. What conditions are triggering it? What dependencies are at play? I need to get to the root cause to understand its purpose and how to interact with it effectively. That's the only way to work with this properly.

20/2

2026/08/04 07:18

tool

grepper

Args:

{
  "Expression": "select BLK_CGROUP_PUNT_BIO"
}

Results:

{
  "Output": "fs/btrfs/Kconfig=3=config BTRFS_FS\nfs/btrfs/Kconfig-4-\ttristate \"Btrfs filesystem support\"\nfs/btrfs/Kconfig:5:\tselect BLK_CGROUP_PUNT_BIO\nfs/btrfs/Kconfig-6-\tselect CRC32\n"
}

21/2

2026/08/04 07:18

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 22771
							output: 26
							thoughts: 42

Thoughts:

Okay, here's my interpretation of those thoughts, considering my expertise:

**Checking the BTRFS and Block CGroups**

Alright, it looks like the configuration process has landed on `BTRFS_FS`. Excellent. So the system logic is selecting this, and it makes sense. I can go ahead and incorporate `BTRFS_FS` directly into the configurations. That's a straightforward step.

Now, let's turn our attention to `BLK_CGROUP_FC_APPID`. I need to ensure that the proper controls are in place and that those are properly configured as well. This will impact the overall performance and resource allocation, so it's critical to verify its setup.

22/2

2026/08/04 07:18

tool

grepper

Args:

{
  "Expression": "config BLK_CGROUP_FC_APPID"
}

Results:

{
  "Output": "block/Kconfig=134=config BLK_CGROUP_IOLATENCY\n--\nblock/Kconfig-144-\nblock/Kconfig:145:config BLK_CGROUP_FC_APPID\nblock/Kconfig-146-\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n"
}

23/2

2026/08/04 07:18

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 23083
							output: 32
							thoughts: 29

Thoughts:

Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person:

**Navigating the Storage Protocol Labyrinth**

Alright, so the immediate question at hand hinges on the underlying storage protocol in play here. My initial thought process is to determine if we're dealing with `NVME_FC` or `SCSI_FC_ATTRS`. This is the critical juncture for this line of inquiry.

Given this dependency, my next step is a deep dive into the `block/Kconfig` configuration file. That's where I need to confirm the conditions for the inclusion of the functionality. Understanding the Kconfig dependencies will immediately clarify the configuration path and relevant configurations. From there, I can determine the appropriate steps for the required modifications.

24/2

2026/08/04 07:18

tool

read-file

Args:

{
  "File": "block/Kconfig",
  "FirstLine": 140,
  "LineCount": 20
}

Results:

{
  "Contents": " 140:\t\tthe configured latency target, throttling anybody with a higher latency\n 141:\t\ttarget than the victimized group.\n 142:\t\n 143:\t\tNote, this is an experimental interface and could be changed someday.\n 144:\t\n 145:\tconfig BLK_CGROUP_FC_APPID\n 146:\t\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n 147:\t\tdepends on BLK_CGROUP \u0026\u0026 NVME_FC\n 148:\t\thelp\n 149:\t\t  Enabling this option enables the support to track FC I/O traffic across\n 150:\t\t  cgroup applications. It enables the Fabric and the storage targets to\n 151:\t\t  identify, monitor, and handle FC traffic based on VM tags by inserting\n 152:\t\t  application specific identification into the FC frame.\n 153:\t\n 154:\tconfig BLK_CGROUP_IOCOST\n 155:\t\tbool \"Enable support for cost model based cgroup IO controller\"\n 156:\t\tdepends on BLK_CGROUP\n 157:\t\tselect BLK_RQ_ALLOC_TIME\n 158:\t\thelp\n 159:\t\tEnabling this option enables the .weight interface for cost\n"
}

25/2

2026/08/04 07:18

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 23638
							output: 32
							thoughts: 38

Thoughts:

Okay, here's my interpretation of those thoughts, presented as my own mental process, with the assumption I'm an expert in this field.

**Navigating Storage and Control Groups**

Alright, so it's clear that we're dealing with a specific interaction here. It seems the `NVME_FC` functionality is a prerequisite for correctly handling `BLK_CGROUP_FC_APPID`. That makes sense; the NVMe-FC protocol likely sets up the foundational framework for flow control and application ID management at a higher level, potentially interacting with the cgroup configuration. I need to make sure I understand the dependencies clearly.

Now, let's pivot to a related area. Since we're in this space, I need to take a look at how `BLK_CGROUP_IOPRIO` interacts with the configuration as well. It could be that the flow control settings and the I/O priority settings should be integrated in a certain way. This check is crucial for optimizing overall performance and preventing conflicts. Gotta make sure everything is cohesive within the cgroup and storage setup. Let's see how these interact.

26/2

2026/08/04 07:18

tool

read-file

Args:

{
  "File": "block/Kconfig",
  "FirstLine": 160,
  "LineCount": 20
}

Results:

{
  "Contents": " 160:\t\tmodel based proportional IO control.  The IO controller\n 161:\t\tdistributes IO capacity between different groups based on\n 162:\t\ttheir share of the overall weight distribution.\n 163:\t\n 164:\tconfig BLK_CGROUP_IOPRIO\n 165:\t\tbool \"Cgroup I/O controller for assigning an I/O priority class\"\n 166:\t\tdepends on BLK_CGROUP\n 167:\t\thelp\n 168:\t\tEnable the .prio interface for assigning an I/O priority class to\n 169:\t\trequests. The I/O priority class affects the order in which an I/O\n 170:\t\tscheduler and block devices process requests. Only some I/O schedulers\n 171:\t\tand some block devices support I/O priorities.\n 172:\t\n 173:\tconfig BLK_DEBUG_FS\n 174:\t\tbool \"Block layer debugging information in debugfs\"\n 175:\t\tdefault y\n 176:\t\tdepends on DEBUG_FS\n 177:\t\thelp\n 178:\t\tInclude block layer debugging information in debugfs. This information\n 179:\t\tis mostly useful for kernel developers, but it doesn't incur any cost\n"
}

27/2

2026/08/04 07:18

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 24269
							output: 19
							thoughts: 115

Thoughts:

**Analyzing Block Device Configuration Options**

Alright, let's take a look at these block device configurations. I see we've got a list here: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, then `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, and some NVMe and Btrfs options with `NVME_FC`, `BLK_CGROUP_FC_APPID`, and `BTRFS_FS`. My initial thought is to quickly ascertain any potential dependencies, to better understand how these pieces fit together. For starters, let me check into `NVME_FC` specifically. That's a good place to begin my analysis.

28/2

2026/08/04 07:18

tool

grepper

Args:

{
  "Expression": "config NVME_FC"
}

Results:

{
  "Output": "drivers/nvme/host/Kconfig=52=config NVME_RDMA\n--\ndrivers/nvme/host/Kconfig-66-\ndrivers/nvme/host/Kconfig:67:config NVME_FC\ndrivers/nvme/host/Kconfig-68-\ttristate \"NVM Express over Fabrics FC host driver\"\n"
}

29/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 24672
							output: 36
							thoughts: 15

Thoughts:

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Diving into the NVMe Host Kconfig**

Alright, let's crack open `drivers/nvme/host/Kconfig`. This is where the core configuration options for the NVMe host controller driver reside, and understanding this file is key to customizing and optimizing its behavior. I need to refresh my memory on the specific configuration knobs available.

First, I'll be looking for any architectural assumptions or dependencies it defines, particularly relating to the platform's interrupt handling. Are there any processor-specific sections I need to keep in mind, or is this largely platform-agnostic?

Next, I'll scan for options related to features like multi-queue support, AER (Advanced Error Reporting), and potentially even specific NVMe version support if there's any branching in the code. I'll need to pay close attention to the default values and help text for each option. These defaults often expose the project's priorities and the typical target hardware.

I'll be checking if there are any specific options tied to specific vendor controllers, to know what hardware is fully supported and what requires a bit of customization. I'll be particularly interested in the option dependencies and their implications. Are there options that imply a certain hardware configuration? What are the implications of enabling or disabling them, especially in terms of performance and power consumption?

Finally, I'll need to keep an eye out for any "tricky" bits – conditional compilation based on other kernel configurations, potential conflicts, or anything that could subtly affect the driver's integration with the rest of the storage stack. The goal here is to get a handle on the available configuration space and how to effectively leverage it for a given deployment scenario.

30/2

2026/08/04 07:19

tool

read-file

Args:

{
  "File": "drivers/nvme/host/Kconfig",
  "FirstLine": 60,
  "LineCount": 20
}

Results:

{
  "Contents": "  60:\t\t  to use remote block devices exported using the NVMe protocol set.\n  61:\t\n  62:\t\t  To configure a NVMe over Fabrics controller use the nvme-cli tool\n  63:\t\t  from https://github.com/linux-nvme/nvme-cli.\n  64:\t\n  65:\t\t  If unsure, say N.\n  66:\t\n  67:\tconfig NVME_FC\n  68:\t\ttristate \"NVM Express over Fabrics FC host driver\"\n  69:\t\tdepends on BLOCK\n  70:\t\tdepends on HAS_DMA\n  71:\t\tselect NVME_FABRICS\n  72:\t\tselect SG_POOL\n  73:\t\thelp\n  74:\t\t  This provides support for the NVMe over Fabrics protocol using\n  75:\t\t  the FC transport.  This allows you to use remote block devices\n  76:\t\t  exported using the NVMe protocol set.\n  77:\t\n  78:\t\t  To configure a NVMe over Fabrics controller use the nvme-cli tool\n  79:\t\t  from https://github.com/linux-nvme/nvme-cli.\n"
}

31/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 25385
							output: 20
							thoughts: 23

Thoughts:

Here's my take on those thoughts:

**Evaluating Storage Options**

Alright, so `NVME_FC` seems like a solid choice for now. That meets the fundamental performance requirements. But, I need to take a wider look at the system to ensure I haven't missed any edge cases and performance bottlenecks.

I should also evaluate `BTRFS_FS`, especially given its flexibility and data management features. I need to make sure I'm not overlooking a better solution for this particular scenario, considering the long-term implications and potential for future expansion or optimization.

32/2

2026/08/04 07:19

tool

grepper

Args:

{
  "Expression": "config BTRFS_FS"
}

Results:

{
  "Output": "fs/btrfs/Kconfig-2-\nfs/btrfs/Kconfig:3:config BTRFS_FS\nfs/btrfs/Kconfig-4-\ttristate \"Btrfs filesystem support\"\n--\nfs/btrfs/Kconfig-38-\nfs/btrfs/Kconfig:39:config BTRFS_FS_POSIX_ACL\nfs/btrfs/Kconfig-40-\tbool \"Btrfs POSIX Access Control Lists\"\n--\nfs/btrfs/Kconfig-48-\nfs/btrfs/Kconfig:49:config BTRFS_FS_RUN_SANITY_TESTS\nfs/btrfs/Kconfig-50-\tbool \"Btrfs will run sanity tests upon loading\"\n"
}

33/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 25744
							output: 21
							thoughts: 23

Thoughts:

Here's my take on those thoughts:

**Evaluating the Storage Setup**

Okay, so `BTRFS_FS` is confirmed. No immediate red flags there. Now, the next logical step is to delve into the I/O scheduler. Let's see how `IOSCHED_BFQ` is performing within this specific configuration. I need to understand its impact on overall system performance and how it interacts with `BTRFS`. There could be subtle interactions I need to identify.

34/2

2026/08/04 07:19

tool

grepper

Args:

{
  "Expression": "config IOSCHED_BFQ"
}

Results:

{
  "Output": "block/Kconfig.iosched=10=config MQ_IOSCHED_KYBER\n--\nblock/Kconfig.iosched-18-\nblock/Kconfig.iosched:19:config IOSCHED_BFQ\nblock/Kconfig.iosched-20-\ttristate \"BFQ I/O scheduler\"\n"
}

35/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 25981
							output: 23
							thoughts: 26

Thoughts:

Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person:

**Kernel I/O Scheduler Assessment**

Alright, so `IOSCHED_BFQ` – that's looking good, as expected. Seems like the base BFQ implementation is holding its own. However, I need to dig a little deeper. The true test is often how these schedulers handle the more complex group structures. So, I'm going to shift my focus. Let's get into investigating `BFQ_GROUP_IOSCHED`. The grouping aspect is where things get really interesting, and where we'll likely uncover any hidden performance bottlenecks or scalability issues related to how BFQ deals with I/O isolation between different application groups. That's the key now.

36/2

2026/08/04 07:19

tool

grepper

Args:

{
  "Expression": "config BFQ_GROUP_IOSCHED"
}

Results:

{
  "Output": "block/Kconfig.iosched=19=config IOSCHED_BFQ\n--\nblock/Kconfig.iosched-29-\nblock/Kconfig.iosched:30:config BFQ_GROUP_IOSCHED\nblock/Kconfig.iosched-31-       bool \"BFQ hierarchical scheduling support\"\n"
}

37/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 26284
							output: 34
							thoughts: 28

Thoughts:

Okay, here's my summary, expressed as though I'm thinking it:

**Thinking Through BFQ's Dependencies**

Alright, let's break this down. *BFQ_GROUP_IOSCHED*... right, that's the thing that lets us do I/O scheduling per cgroup. Makes sense. But it's not a standalone feature, is it? It relies heavily on *IOSCHED_BFQ*, the actual BFQ scheduler itself. We can't have per-cgroup BFQ without the base BFQ functionality. And further, if we're doing cgroup-based scheduling, then *BLK_CGROUP* is absolutely foundational. It's the infrastructure that provides the whole cgroup hierarchy and resource management framework for block devices in the first place. So, without BLK_CGROUP, IOSCHED_BFQ wouldn't work, and neither would BFQ_GROUP_IOSCHED. It's a clear dependency chain: cgroups, then the scheduler, then the group scheduler implementation. Got it.

38/2

2026/08/04 07:19

tool

read-file

Args:

{
  "File": "block/Kconfig.iosched",
  "FirstLine": 25,
  "LineCount": 20
}

Results:

{
  "Contents": "  25:\t\tregardless of the device parameters and with any workload. It\n  26:\t\talso guarantees a low latency to interactive and soft\n  27:\t\treal-time applications.  Details in\n  28:\t\tDocumentation/block/bfq-iosched.rst\n  29:\t\n  30:\tconfig BFQ_GROUP_IOSCHED\n  31:\t       bool \"BFQ hierarchical scheduling support\"\n  32:\t       depends on IOSCHED_BFQ \u0026\u0026 BLK_CGROUP\n  33:\t       default y\n  34:\t       select BLK_CGROUP_RWSTAT\n  35:\t\thelp\n  36:\t\n  37:\t       Enable hierarchical scheduling in BFQ, using the blkio\n  38:\t       (cgroups-v1) or io (cgroups-v2) controller.\n  39:\t\n  40:\tconfig BFQ_CGROUP_DEBUG\n  41:\t\tbool \"BFQ IO controller debugging\"\n  42:\t\tdepends on BFQ_GROUP_IOSCHED\n  43:\t\thelp\n  44:\t\tEnable some debugging help. Currently it exports additional stat\n"
}

39/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 26864
							output: 32
							thoughts: 308

Thoughts:

**Analyzing Block I/O Cgroup Configuration Options**

Alright, I've got a solid list of block I/O cgroup configuration options to consider. We have `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, and `BTRFS_FS`. This looks like a good starting point for understanding how different features interact.

Now, from what I recall, `bio_blkg_lookup` and `bio_blkg` are the core functions here. I need to make sure I haven't missed any other crucial functions though. Let me quickly scan for related functions... Okay, I see `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`. This seems like a reasonable set of supporting functions.

Good, now to see if `bio_put_blkg_ref` is exported. Yes, it looks like it is, which is important for external modules to interact with it.

I should probably double-check the configs one more time, to make sure there are no other dependencies I need to be aware of. Okay, `CONFIG_BLK_CGROUP_PUNT_BIO` is selected by `BTRFS_FS`, that's a key interaction to remember. I also see that `CONFIG_BLK_CGROUP_FC_APPID` depends on either `NVME_FC` or `SCSI_FC_ATTRS`. Wait, let me just confirm the exact dependencies for `BLK_CGROUP_FC_APPID` so I can fully understand this.

40/2

2026/08/04 07:19

tool

read-file

Args:

{
  "File": "block/Kconfig",
  "FirstLine": 140,
  "LineCount": 10
}

Results:

{
  "Contents": " 140:\t\tthe configured latency target, throttling anybody with a higher latency\n 141:\t\ttarget than the victimized group.\n 142:\t\n 143:\t\tNote, this is an experimental interface and could be changed someday.\n 144:\t\n 145:\tconfig BLK_CGROUP_FC_APPID\n 146:\t\tbool \"Enable support to track FC I/O Traffic across cgroup applications\"\n 147:\t\tdepends on BLK_CGROUP \u0026\u0026 NVME_FC\n 148:\t\thelp\n 149:\t\t  Enabling this option enables the support to track FC I/O traffic across\n"
}

41/2

2026/08/04 07:19

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 27796
							output: 17
							thoughts: 59

Thoughts:

Okay, here's my interpretation of those thoughts, tailored for an expert audience, as if they were my own mental process:

**Configuration Dependency Deep Dive**

Right, this is about the `BLK_CGROUP` and `NVME_FC` configs. It's clear that the code flow relies on `NVME_FC` being enabled; that's a given. I need to figure out what other dependencies might exist. Specifically, the mention of `CONFIG_MEMCG` in `mm/page_io.c` has caught my eye. It's often the case that seemingly unrelated subsystems share dependencies, especially when you're dealing with block I/O and memory management. It's likely that if `MEMCG` is enabled there are implications for how `NVME_FC` interacts with it. That could open an interesting rabbit hole that needs to be explored. Let's see what the interactions are.

42/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "config MEMCG"
}

Results:

{
  "Output": "init/Kconfig=1066=config CGROUP_FAVOR_DYNMODS\n--\ninit/Kconfig-1075-\ninit/Kconfig:1076:config MEMCG\ninit/Kconfig-1077-\tbool \"Memory controller\"\n--\ninit/Kconfig-1084-\ninit/Kconfig:1085:config MEMCG_NMI_UNSAFE\ninit/Kconfig-1086-\tbool\n--\ninit/Kconfig-1091-\ninit/Kconfig:1092:config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC\ninit/Kconfig-1093-\tbool\n--\ninit/Kconfig-1098-\ninit/Kconfig:1099:config MEMCG_V1\ninit/Kconfig-1100-\tbool \"Legacy cgroup v1 memory controller\"\n"
}

43/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 28296
							output: 28
							thoughts: 520

Thoughts:

**Analyzing Hot-Path Functions for Focused Fuzzing**

Okay, so I'm thinking about how to construct the `FocusSymbols` list for fuzzing this code. `MEMCG` is definitely a good starting point. Let's look at the functions that relate to block cgroups.

First, I see: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`.

I have to consider the prompt's instruction to avoid generic hot-path functions to prevent test distributions from being skewed. I know `bio_blkg_lookup` and `bio_blkg` are called frequently on the I/O path. `bio_associate_blkcg` is in `bio_init`, `bio_reset` and `bio_set_dev`. `bio_clone_blkcg_association` is in `__bio_clone`. `bio_put_blkg_ref` is in `bio_clear_blkcg`, which is called in `bio_uninit` and `bio_endio`. These are very hot-path. But, the prompt *specifically* tells me to prioritize non-static, non-inlined API entrypoints functions, so these would be good.

However, `bio_blkg` and `bio_blkg_lookup` are *specific* to block cgroups and are new or modified by this patch. While hot-path for block I/O, they are the very functions I want to focus on. So, I think I'll include them. The prompt says to avoid generic hot-path functions, but `bio_blkg` and `bio_blkg_lookup` are the main new functions and are exactly what I need to focus the fuzzing on.

`blkcg_punt_bio_submit` is another one. It's called when bouncing bios for cgroups, which makes it less hot-path. I think that is still okay to include. `bfq_bio_bfqg` is specific to BFQ, which is another interesting candidate, and I'll include `blkcg_get_fc_appid` as well, as that's FC appid specific.

So, I'm going to include: `bio_blkg`, `bio_blkg_lookup`, `blkcg_punt_bio_submit`, `blkcg_get_fc_appid`, and `bfq_bio_bfqg`. Now, let's just make sure that `bfq_bio_bfqg` is exported and non-static...

44/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "struct bfq_group \\*bfq_bio_bfqg"
}

Results:

{
  "Output": "block/bfq-cgroup.c=586=static void bfq_link_bfqg(struct bfq_data *bfqd, struct bfq_group *bfqg)\n--\nblock/bfq-cgroup.c-608-\nblock/bfq-cgroup.c:609:struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)\nblock/bfq-cgroup.c-610-{\n--\nblock/bfq-cgroup.c=1439=void bfq_end_wr_async(struct bfq_data *bfqd)\n--\nblock/bfq-cgroup.c-1445-\nblock/bfq-cgroup.c:1446:struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)\nblock/bfq-cgroup.c-1447-{\n--\nblock/bfq-iosched.h=1086=void bfq_end_wr_async(struct bfq_data *bfqd);\nblock/bfq-iosched.h:1087:struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio);\nblock/bfq-iosched.h-1088-struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);\n"
}

45/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 29806
							output: 24
							thoughts: 21

Thoughts:

Okay, here's my summary, tailored as requested:

**Assessing Dynamic State**

Right, this situation isn't static. We need to understand the moving parts. My initial instinct is to go deeper into a specific function. Let's see... the most relevant function in this context would be `blkcg_get_fc_appid`. Time to dig in and see what's happening there. That's the key to understanding the non-static element.

46/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "char \\*blkcg_get_fc_appid"
}

Results:

{
  "Output": "block/blk-cgroup-fc-appid.c=43=EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);\n--\nblock/blk-cgroup-fc-appid.c-50- */\nblock/blk-cgroup-fc-appid.c:51:char *blkcg_get_fc_appid(struct bio *bio)\nblock/blk-cgroup-fc-appid.c-52-{\n--\ninclude/linux/blk-cgroup.h=48=int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len);\ninclude/linux/blk-cgroup.h:49:char *blkcg_get_fc_appid(struct bio *bio);\ninclude/linux/blk-cgroup.h-50-\n"
}

47/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 30162
							output: 23
							thoughts: 18

Thoughts:

Okay, here's my take on those thoughts, tailored for an expert audience:

**Analyzing the Exported Function**

Right, so it's been flagged as "exported." That immediately triggers a mental checklist: what's the context? What is *exported*? Is it a kernel symbol, a userspace interface, a module export, or something else entirely? The implications are vastly different depending on the specific situation. The level of abstraction here is key - what is being exported, and where is it going?

My immediate follow-up thought is to dive into the particulars of `blkcg_set_ioprio`. This function name itself already tells a story. "blkcg" suggests block I/O control groups. So, this probably deals with setting I/O priorities within a control group context. Now I need to consider, from an expert's point of view: Are we talking about the original cgroup v1 implementation, or the newer cgroup v2? What about the specific data structures involved? Is it related to the `ioprio` class, and its associated parameters? Or is it a part of scheduling or bandwidth enforcement, etc? And how does this connect to my current line of thinking and my project goals. I need to refresh the knowledge of the implementation so that I am familiar with the latest changes and improvements. I have a long list of things to consider. I hope it is all up-to-date.

48/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "void blkcg_set_ioprio"
}

Results:

{
  "Output": "block/blk-ioprio.c=125=static struct blkcg_policy ioprio_policy = {\n--\nblock/blk-ioprio.c-132-\nblock/blk-ioprio.c:133:void blkcg_set_ioprio(struct bio *bio)\nblock/blk-ioprio.c-134-{\n--\nblock/blk-ioprio.h=9=struct bio;\n--\nblock/blk-ioprio.h-11-#ifdef CONFIG_BLK_CGROUP_IOPRIO\nblock/blk-ioprio.h:12:void blkcg_set_ioprio(struct bio *bio);\nblock/blk-ioprio.h-13-#else\nblock/blk-ioprio.h:14:static inline void blkcg_set_ioprio(struct bio *bio)\nblock/blk-ioprio.h-15-{\n"
}

49/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 30730
							output: 24
							thoughts: 34

Thoughts:

Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person:

**Analyzing Dynamic IO Behavior**

Right, this isn't a static situation. I need to dig deeper. Something's clearly fluctuating, and I'm guessing it has to do with how IO latency is managed. Let's see... my initial instinct is to drill down into the control group IO latency mechanisms. I'll need to examine the interactions of `blkcg_iolatency_throttle` and `blkcg_iolatency_done_bio` particularly. These are the key functions responsible for throttling IO based on latency targets and signaling completion. I need to understand the sequencing and the potential bottlenecks within those. Perhaps there's a runaway condition, a miscalculation somewhere, or even contention for resources. Let's pull up the code and dive in. I need to understand what's *actually* happening at that level to pinpoint the root cause.

50/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "void blkcg_iolatency_throttle"
}

Results:

{
  "Output": "block/blk-iolatency.c=399=static void check_scale_change(struct iolatency_grp *iolat)\n--\nblock/blk-iolatency.c-462-\nblock/blk-iolatency.c:463:static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)\nblock/blk-iolatency.c-464-{\n"
}

51/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 31109
							output: 22
							thoughts: 35

Thoughts:

Okay, here's my interpretation of those thoughts, crafted with the understanding that I'm discussing this with a fellow expert:

**Internal Review of IO QoS Handling**

Alright, the current picture seems...fixed. Stagnant. I need to make sure I'm not missing something fundamental. This feels like the kind of situation where a subtle oversight could cause big problems later on, so let's start with a systematic review. Let's see if there are any obvious issues.

My immediate focus then shifts to those specific functions: `ioc_rqos_throttle`, `ioc_rqos_merge`, and `ioc_rqos_done_bio`. I need to re-examine how these functions are handling the I/O QoS aspects. Are the throttling mechanisms behaving as expected under various workloads? What about the merging logic? And, of course, how are we signaling completion? There could be a subtle race condition in any of these. I need to verify how these interact. I need to fully understand if there are any holes in the logic in any of these, given the state of the system that I see currently.

52/2

2026/08/04 07:20

tool

grepper

Args:

{
  "Expression": "void ioc_rqos_throttle"
}

Results:

{
  "Output": "block/blk-iocost.c=2613=iocg_handle_over_budget(struct rq_qos *rqos, struct ioc_gq *iocg,\n--\nblock/blk-iocost.c-2686-\nblock/blk-iocost.c:2687:static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)\nblock/blk-iocost.c-2688-{\n"
}

53/2

2026/08/04 07:20

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 31525
							output: 22
							thoughts: 18

Thoughts:

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Assessing a Potential Bottleneck**

Hmm, things feel…stuck. Static. That's never good, especially when performance is on the line. I need to pinpoint the constraint. Let's dig into the details. My gut tells me this could be a throttling issue. I immediately think of the block layer. Specifically, I should check `__blk_throtl_bio`. That's where I'd expect to find the queueing logic and any potential bottlenecks related to I/O scheduling and prioritization. It's a key function for understanding how I/O requests are handled, and checking its state will give me a very solid starting point to diagnose any performance issues.

54/2

2026/08/04 07:21

tool

grepper

Args:

{
  "Expression": "bool __blk_throtl_bio"
}

Results:

{
  "Output": "block/blk-throttle.c=1764=static bool tg_within_limit(struct throtl_grp *tg, struct bio *bio, bool rw)\n--\nblock/blk-throttle.c-1791-\nblock/blk-throttle.c:1792:bool __blk_throtl_bio(struct bio *bio)\nblock/blk-throttle.c-1793-{\n--\nblock/blk-throttle.h=153=void blk_throtl_exit(struct gendisk *disk);\nblock/blk-throttle.h:154:bool __blk_throtl_bio(struct bio *bio);\nblock/blk-throttle.h-155-void blk_throtl_cancel_bios(struct gendisk *disk);\n"
}

55/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 31924
							output: 26
							thoughts: 348

Thoughts:

**Analyzing Block IO and Control Group Interactions**

Okay, so I'm looking at this code and it's definitely dynamic, not static. I need to figure out the key functions related to block IO and control group (blkcg) association. Let's see... I'll check what's exported and relevant.

Right, `bio_blkg_lookup` and `bio_blkg` are both exported, which is a good starting point. Then we have `bio_associate_blkcg_from_css` and `bio_associate_blkcg` which are also exported - interesting. Plus, there's `bio_clone_blkcg_association` and `bio_put_blkg_ref` that are exported.

Based on that, I'd say the "FocusSymbols" should include:

*   `bio_blkg_lookup`
*   `bio_blkg`
*   `bio_associate_blkcg_from_css`
*   `bio_associate_blkcg`
*   `bio_clone_blkcg_association`
*   `bio_put_blkg_ref`
*   `blkcg_punt_bio_submit`
*   `bfq_bio_bfqg`
*   `blkcg_get_fc_appid`
*   `blkcg_set_ioprio`
*   `__blk_throtl_bio`

Wait a minute, `bio_associate_blkcg_from_css` seems like it could be a crucial, hot-path function, but it's being specifically modified here. I think focusing in on the following functions would make the most sense for the current task: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, and `blkcg_punt_bio_submit`.

Let me quickly look at `bio_associate_blkcg_from_page` though. Okay, so it's a static function, defined within `mm/page_io.c`. Not directly relevant here, but good to know. And let's also check out `bfqg_stats_update_legacy_io`.

56/2

2026/08/04 07:21

tool

grepper

Args:

{
  "Expression": "void bfqg_stats_update_legacy_io"
}

Results:

{
  "Output": "block/bfq-cgroup.c=357=void bfqg_and_blkg_put(struct bfq_group *bfqg)\n--\nblock/bfq-cgroup.c-363-\nblock/bfq-cgroup.c:364:void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq)\nblock/bfq-cgroup.c-365-{\n--\nblock/bfq-iosched.h=1060=void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);\n--\nblock/bfq-iosched.h-1065-\nblock/bfq-iosched.h:1066:void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq);\nblock/bfq-iosched.h-1067-void bfqg_stats_update_io_remove(struct bfq_group *bfqg, blk_opf_t opf);\n"
}

57/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 33065
							output: 24
							thoughts: 21

Thoughts:

Okay, here's my attempt at summarizing those thoughts from a first-person, expert perspective, aiming for a fulsome rendering:

**Analyzing the Dynamic Nature**

Right, this situation is not static. That's the first thing that jumps out at me. We're dealing with a dynamic process, and understanding its evolution is key. I need to dig deeper into the root cause. This isn't a one-off event.

The next step is clear: I need to investigate what's happening internally, and the best place to start is often at the beginning. Let's start by looking at `blk_cgroup_bio_start`. I have a feeling that function will provide some crucial insights into the initial conditions, control mechanisms, or potential for unexpected behavior in this evolving system. From there, I can trace its impact through the relevant code paths. It's the logical starting point for understanding this dynamic process.

58/2

2026/08/04 07:21

tool

grepper

Args:

{
  "Expression": "void blk_cgroup_bio_start"
}

Results:

{
  "Output": "block/blk-cgroup.c=2223=static int blk_cgroup_io_type(struct bio *bio)\n--\nblock/blk-cgroup.c-2231-\nblock/blk-cgroup.c:2232:void blk_cgroup_bio_start(struct bio *bio)\nblock/blk-cgroup.c-2233-{\n--\nblock/blk-cgroup.h=480=static inline bool blkcg_policy_enabled(struct request_queue *q,\n--\nblock/blk-cgroup.h-485-\nblock/blk-cgroup.h:486:void blk_cgroup_bio_start(struct bio *bio);\nblock/blk-cgroup.h-487-void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta);\n--\nblock/blk-cgroup.h=521=static inline void bio_clear_blkcg(struct bio *bio) { }\nblock/blk-cgroup.h:522:static inline void blk_cgroup_bio_start(struct bio *bio) { }\nblock/blk-cgroup.h-523-static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }\n"
}

59/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 33643
							output: 21
							thoughts: 342

Thoughts:

**Refining the Block I/O Cgroup Focus**

Okay, this needs to be dynamic, not static. I need to make sure I'm capturing everything correctly for the Block I/O Cgroup analysis. First, I need to refine that `FocusSymbols` list. Let's see... I'll start with this group:

`bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, `bfq_bio_bfqg`, `blkcg_get_fc_appid`, `blkcg_set_ioprio`, `__blk_throtl_bio`, `bfqg_stats_update_legacy_io`, `blk_cgroup_bio_start`.

Wait a minute, `bio_associate_blkcg_from_css` really is a key function here. I'll need to keep that one in mind. Now, I should make sure I haven't missed any related configuration options. Looking at that `bio_associate_blkcg_from_page` function in `mm/page_io.c`, it looks like `CONFIG_MEMCG` is required for that particular function. I'll need to add `MEMCG` to my configuration list.

So, here's my updated configuration list to consider:
`BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, `BTRFS_FS` and finally, that important `MEMCG` setting.

Now I need to check how `CONFIG_CGROUP_WRITEBACK` might fit in.

60/2

2026/08/04 07:21

tool

grepper

Args:

{
  "Expression": "config CGROUP_WRITEBACK"
}

Results:

{
  "Output": "init/Kconfig=1116=config BLK_CGROUP\n--\ninit/Kconfig-1137-\ninit/Kconfig:1138:config CGROUP_WRITEBACK\ninit/Kconfig-1139-\tbool\n"
}

61/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 34515
							output: 21
							thoughts: 15

Thoughts:

Here's my attempt at summarizing the thought process, tailored for an expert audience:

**Analyzing a Boolean Flag**

Okay, so I've stumbled upon a hidden boolean variable. My initial instinct is to dig deeper and understand its purpose and behavior. My primary focus right now is to identify all the points in the code that are reading or writing to this flag. I need to trace back from where it's defined and figure out what logic paths are controlling its state. Is it being set based on a specific input, a calculation, a condition, a user action, a data event? Or maybe a combination of these elements? Once I understand the selectors, then I can ascertain its purpose.

62/2

2026/08/04 07:21

tool

grepper

Error:

no matches

Args:

{
  "Expression": "select CGROUP_WRITEBACK"
}

Results:

{
  "error": "no matches"
}

63/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 34708
							output: 33
							thoughts: 21

Thoughts:

Here's my thought process, as if I were considering this myself:

**Kconfig Dive for CGROUP_WRITEBACK**

Okay, before I go any further down this rabbit hole, I need to verify something fundamental. I should probably double check the `init/Kconfig` file in the kernel source. Specifically, I need to confirm whether or not `CGROUP_WRITEBACK` is defined. This option is critical for [insert your field's relevance to cgroup writeback here - e.g., enabling background data flushing in my storage subsystem work], and I need to make sure I understand its current state before moving on to consider its usage or implications further. Without this verification, I could waste time investigating something that may not even be present or enabled in the current configuration. Gotta check the Kconfig.

64/2

2026/08/04 07:21

tool

read-file

Args:

{
  "File": "init/Kconfig",
  "FirstLine": 1130,
  "LineCount": 20
}

Results:

{
  "Contents": "1130:\t\tThis option only enables generic Block IO controller infrastructure.\n1131:\t\tOne needs to also enable actual IO controlling logic/policy. For\n1132:\t\tenabling proportional weight division of disk bandwidth in CFQ, set\n1133:\t\tCONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set\n1134:\t\tCONFIG_BLK_DEV_THROTTLING=y.\n1135:\t\n1136:\t\tSee Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.\n1137:\t\n1138:\tconfig CGROUP_WRITEBACK\n1139:\t\tbool\n1140:\t\tdepends on MEMCG \u0026\u0026 BLK_CGROUP\n1141:\t\tdefault y\n1142:\t\n1143:\tmenuconfig CGROUP_SCHED\n1144:\t\tbool \"CPU controller\"\n1145:\t\tdefault n\n1146:\t\thelp\n1147:\t\t  This feature lets CPU scheduler recognize task groups and control CPU\n1148:\t\t  bandwidth allocation to such task groups. It uses cgroups to group\n1149:\t\t  tasks.\n"
}

65/2

2026/08/04 07:21

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 35243
							output: 24
							thoughts: 57

Thoughts:

**My Configuration Musings**

Okay, so I see this default behavior when both `MEMCG` and `BLK_CGROUP` are enabled, defaulting to 'y'. That simplifies things a bit; it means if those two are set, we're likely good. My focus is narrowed.

Now, let's just confirm. I need to take a look at `CONFIG_BLK_DEV_THROTTLING`. That's where the real magic happens, so I'll see what the configuration there tells us.

66/2

2026/08/04 07:21

tool

grepper

Args:

{
  "Expression": "config BLK_DEV_THROTTLING"
}

Results:

{
  "Output": "block/Kconfig=97=config BLK_DEV_ZONED\n--\nblock/Kconfig-105-\nblock/Kconfig:106:config BLK_DEV_THROTTLING\nblock/Kconfig-107-\tbool \"Block layer bio throttling support\"\n"
}

67/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 35517
							output: 26
							thoughts: 47

Thoughts:

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Adding Block Device Throttling Support**

Right, so I see we need this for `__blk_throtl_bio`. Makes perfect sense. Seems like the logical next step is to add `BLK_DEV_THROTTLING`. That'll give us the foundation we need. Now, let me just quickly double-check... I need to make sure we consider the implications of `CONFIG_BLK_DEV_THROTTLING_LOW`, because depending on how that's defined, it will affect how this functions. Gotta make sure we cover all our bases.

68/2

2026/08/04 07:22

tool

grepper

Error:

no matches

Args:

{
  "Expression": "config BLK_DEV_THROTTLING_LOW"
}

Results:

{
  "error": "no matches"
}

69/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 35746
							output: 16
							thoughts: 25

Thoughts:

Okay, here's my take on those seemingly simple thoughts:

**Dissecting the Kernel Configuration Landscape**

Right, so, the focus is clearly on kernel configuration, specifically related to storage or block device management. The phrase `BLK_DEV_THROTTLING` immediately triggers a mental scan. My initial assessment is that this is the core concern, likely indicating a need to manage I/O performance on block devices, potentially to prevent resource starvation or maintain quality of service. It's a fundamental aspect of system stability and responsiveness, so it makes sense to nail this down first.

Now, the follow-up, `CONFIG_MD`. Ah, this is telling. The jump to `CONFIG_MD` (likely meaning Multiple Devices or RAID support) suggests that the throttling might be in the context of a RAID array or some form of logical volume management. We need to consider how the block device throttling interacts with the complexities introduced by data striping, mirroring, and parity calculations. Are we optimizing for a particular RAID level? Is there a performance bottleneck related to how the kernel interacts with the underlying physical devices in the array? This calls for careful examination. This is all about balancing the needs of different components.

70/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config MD"
}

Results:

{
  "Output": "drivers/clk/qcom/Kconfig=563=config MSM_LCC_8960\n--\ndrivers/clk/qcom/Kconfig-571-\ndrivers/clk/qcom/Kconfig:572:config MDM_GCC_9607\ndrivers/clk/qcom/Kconfig-573-\ttristate \"MDM9607 Global Clock Controller\"\n--\ndrivers/clk/qcom/Kconfig-579-\ndrivers/clk/qcom/Kconfig:580:config MDM_GCC_9615\ndrivers/clk/qcom/Kconfig-581-\ttristate \"MDM9615 Global Clock Controller\"\n--\ndrivers/md/Kconfig-5-\ndrivers/md/Kconfig:6:menuconfig MD\ndrivers/md/Kconfig-7-\tbool \"Multiple devices driver support (RAID and LVM)\"\n--\ndrivers/md/Kconfig=15=config BLK_DEV_MD\n--\ndrivers/md/Kconfig-39-\ndrivers/md/Kconfig:40:config MD_BITMAP\ndrivers/md/Kconfig-41-\tbool \"MD RAID bitmap support\"\n--\ndrivers/md/Kconfig-54-\ndrivers/md/Kconfig:55:config MD_LLBITMAP\ndrivers/md/Kconfig-56-\tbool \"MD RAID lockless bitmap support\"\n--\ndrivers/md/Kconfig-65-\ndrivers/md/Kconfig:66:config MD_AUTODETECT\ndrivers/md/Kconfig-67-\tbool \"Autodetect RAID arrays during kernel boot\"\n--\ndrivers/md/Kconfig-79-\ndrivers/md/Kconfig:80:config MD_BITMAP_FILE\ndrivers/md/Kconfig-81-\tbool \"MD bitmap file support (deprecated)\"\n--\ndrivers/md/Kconfig-90-\ndrivers/md/Kconfig:91:config MD_LINEAR\ndrivers/md/Kconfig-92-\ttristate \"Linear (append) mode\"\n--\ndrivers/md/Kconfig-103-\ndrivers/md/Kconfig:104:config MD_RAID0\ndrivers/md/Kconfig-105-\ttristate \"RAID-0 (striping) mode\"\n--\ndrivers/md/Kconfig-123-\ndrivers/md/Kconfig:124:config MD_RAID1\ndrivers/md/Kconfig-125-\ttristate \"RAID-1 (mirroring) mode\"\n--\ndrivers/md/Kconfig-145-\ndrivers/md/Kconfig:146:config MD_RAID10\ndrivers/md/Kconfig-147-\ttristate \"RAID-10 (mirrored striping) mode\"\n--\ndrivers/md/Kconfig-164-\ndrivers/md/Kconfig:165:config MD_RAID456\ndrivers/md/Kconfig-166-\ttristate \"RAID-4/RAID-5/RAID-6 mode\"\n--\ndrivers/md/Kconfig-201-\ndrivers/md/Kconfig:202:config MD_CLUSTER\ndrivers/md/Kconfig-203-\ttristate \"Cluster Support for MD\"\n--\ndrivers/net/ethernet/Kconfig=13=if ETHERNET\ndrivers/net/ethernet/Kconfig-14-\ndrivers/net/ethernet/Kconfig:15:config MDIO\ndrivers/net/ethernet/Kconfig-16-\ttristate\n--\ndrivers/net/mdio/Kconfig=19=config ACPI_MDIO\n--\ndrivers/net/mdio/Kconfig-23-\ndrivers/net/mdio/Kconfig:24:config MDIO_AIROHA\ndrivers/net/mdio/Kconfig-25-\ttristate \"Airoha AN7583 MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-30-\ndrivers/net/mdio/Kconfig:31:config MDIO_SUN4I\ndrivers/net/mdio/Kconfig-32-\ttristate \"Allwinner sun4i MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-38-\ndrivers/net/mdio/Kconfig:39:config MDIO_XGENE\ndrivers/net/mdio/Kconfig-40-\ttristate \"APM X-Gene SoC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-45-\ndrivers/net/mdio/Kconfig:46:config MDIO_ASPEED\ndrivers/net/mdio/Kconfig-47-\ttristate \"ASPEED MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-58-\ndrivers/net/mdio/Kconfig:59:config MDIO_BITBANG\ndrivers/net/mdio/Kconfig-60-\ttristate \"Bitbanged MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-67-\ndrivers/net/mdio/Kconfig:68:config MDIO_BCM_IPROC\ndrivers/net/mdio/Kconfig-69-\ttristate \"Broadcom iProc MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-76-\ndrivers/net/mdio/Kconfig:77:config MDIO_BCM_UNIMAC\ndrivers/net/mdio/Kconfig-78-\ttristate \"Broadcom UniMAC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-85-\ndrivers/net/mdio/Kconfig:86:config MDIO_CAVIUM\ndrivers/net/mdio/Kconfig-87-\ttristate\ndrivers/net/mdio/Kconfig-88-\ndrivers/net/mdio/Kconfig:89:config MDIO_GPIO\ndrivers/net/mdio/Kconfig-90-\ttristate \"GPIO lib-based bitbanged MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-98-\ndrivers/net/mdio/Kconfig:99:config MDIO_HISI_FEMAC\ndrivers/net/mdio/Kconfig-100-\ttristate \"Hisilicon FEMAC MDIO bus controller\"\n--\ndrivers/net/mdio/Kconfig-105-\ndrivers/net/mdio/Kconfig:106:config MDIO_I2C\ndrivers/net/mdio/Kconfig-107-\ttristate\n--\ndrivers/net/mdio/Kconfig-115-\ndrivers/net/mdio/Kconfig:116:config MDIO_MVUSB\ndrivers/net/mdio/Kconfig-117-\ttristate \"Marvell USB to MDIO Adapter\"\n--\ndrivers/net/mdio/Kconfig-122-\ndrivers/net/mdio/Kconfig:123:config MDIO_MSCC_MIIM\ndrivers/net/mdio/Kconfig-124-\ttristate \"Microsemi MIIM interface support\"\n--\ndrivers/net/mdio/Kconfig-131-\ndrivers/net/mdio/Kconfig:132:config MDIO_MOXART\ndrivers/net/mdio/Kconfig-133-\ttristate \"MOXA ART MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-138-\ndrivers/net/mdio/Kconfig:139:config MDIO_OCTEON\ndrivers/net/mdio/Kconfig-140-\ttristate \"Octeon and some ThunderX SOCs MDIO buses\"\n--\ndrivers/net/mdio/Kconfig-148-\ndrivers/net/mdio/Kconfig:149:config MDIO_PIC64HPSC\ndrivers/net/mdio/Kconfig-150-\ttristate \"PIC64-HPSC/HX MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-156-\ndrivers/net/mdio/Kconfig:157:config MDIO_IPQ4019\ndrivers/net/mdio/Kconfig-158-\ttristate \"Qualcomm IPQ4019 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-164-\ndrivers/net/mdio/Kconfig:165:config MDIO_IPQ8064\ndrivers/net/mdio/Kconfig-166-\ttristate \"Qualcomm IPQ8064 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-172-\ndrivers/net/mdio/Kconfig:173:config MDIO_REALTEK_RTL9300\ndrivers/net/mdio/Kconfig-174-\ttristate \"Realtek RTL9300 MDIO interface support\"\n--\ndrivers/net/mdio/Kconfig-179-\ndrivers/net/mdio/Kconfig:180:config MDIO_REGMAP\ndrivers/net/mdio/Kconfig-181-\ttristate\n--\ndrivers/net/mdio/Kconfig-190-\ndrivers/net/mdio/Kconfig:191:config MDIO_THUNDER\ndrivers/net/mdio/Kconfig-192-\ttristate \"ThunderX SOCs MDIO buses\"\n--\ndrivers/net/mdio/Kconfig=201=comment \"MDIO Multiplexers\"\ndrivers/net/mdio/Kconfig-202-\ndrivers/net/mdio/Kconfig:203:config MDIO_BUS_MUX\ndrivers/net/mdio/Kconfig-204-\ttristate\n--\ndrivers/net/mdio/Kconfig-211-\ndrivers/net/mdio/Kconfig:212:config MDIO_BUS_MUX_MESON_G12A\ndrivers/net/mdio/Kconfig-213-\ttristate \"Amlogic G12a based MDIO bus multiplexer\"\n--\ndrivers/net/mdio/Kconfig-222-\ndrivers/net/mdio/Kconfig:223:config MDIO_BUS_MUX_MESON_GXL\ndrivers/net/mdio/Kconfig-224-\ttristate \"Amlogic GXL based MDIO bus multiplexer\"\n--\ndrivers/net/mdio/Kconfig-233-\ndrivers/net/mdio/Kconfig:234:config MDIO_BUS_MUX_BCM6368\ndrivers/net/mdio/Kconfig-235-\ttristate \"Broadcom BCM6368 MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-244-\ndrivers/net/mdio/Kconfig:245:config MDIO_BUS_MUX_BCM_IPROC\ndrivers/net/mdio/Kconfig-246-\ttristate \"Broadcom iProc based MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-255-\ndrivers/net/mdio/Kconfig:256:config MDIO_BUS_MUX_GPIO\ndrivers/net/mdio/Kconfig-257-\ttristate \"GPIO controlled MDIO bus multiplexers\"\n--\ndrivers/net/mdio/Kconfig-265-\ndrivers/net/mdio/Kconfig:266:config MDIO_BUS_MUX_MULTIPLEXER\ndrivers/net/mdio/Kconfig-267-\ttristate \"MDIO bus multiplexer using kernel multiplexer subsystem\"\n--\ndrivers/net/mdio/Kconfig-277-\ndrivers/net/mdio/Kconfig:278:config MDIO_BUS_MUX_MMIOREG\ndrivers/net/mdio/Kconfig-279-\ttristate \"MMIO device-controlled MDIO bus multiplexers\"\n"
}

71/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 38952
							output: 17
							thoughts: 28

Thoughts:

Okay, here's my take on those thoughts, framed as my own:

**Adding Support for MD and Checking BCACHE**

Right, let's get down to brass tacks. I'm looking at configuring this system, and it's clear that the Multi-Device (MD) subsystem needs to be properly addressed. The first thing that jumps out is the need to enable the `BLK_DEV_MD` configuration option. That's a no-brainer; we need that kernel support if we're going to utilize MD arrays. Okay, noted, and I'll add that right away.

Now, a related area that I need to quickly scan, and which I'm already thinking about is `BCACHE`. It's a technology related to caching, and it is a good idea to perform a quick check and see how it interacts with the current setup. I'll make sure it plays nicely, and isn't something that might introduce conflicts later. Let me make a note to investigate that interaction further.

72/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config BCACHE"
}

Results:

{
  "Output": "drivers/md/bcache/Kconfig-2-\ndrivers/md/bcache/Kconfig:3:config BCACHE\ndrivers/md/bcache/Kconfig-4-\ttristate \"Block device as cache\"\n--\ndrivers/md/bcache/Kconfig-13-\ndrivers/md/bcache/Kconfig:14:config BCACHE_DEBUG\ndrivers/md/bcache/Kconfig-15-\tbool \"Bcache debugging\"\n--\ndrivers/md/bcache/Kconfig-22-\ndrivers/md/bcache/Kconfig:23:config BCACHE_ASYNC_REGISTRATION\ndrivers/md/bcache/Kconfig-24-\tbool \"Asynchronous device registration\"\n"
}

73/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 39393
							output: 21
							thoughts: 20

Thoughts:

Okay, here's my take on those initial thoughts, framed as a concise internal monologue:

**Considering Storage Optimization**

Alright, I'm thinking we should definitely incorporate `BCACHE`. It's a proven solution for accelerating storage performance, and it's something I've had good results with in the past.

Now, before we get too far down that road, I need to double-check the interaction with `BLK_DEV_DM`. It's critical to ensure there are no compatibility conflicts or performance bottlenecks between these two layers. That's the priority at this moment. Let's make sure it is fully compatible before proceeding.

74/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config BLK_DEV_DM"
}

Results:

{
  "Output": "drivers/md/Kconfig=219=source \"drivers/md/bcache/Kconfig\"\ndrivers/md/Kconfig-220-\ndrivers/md/Kconfig:221:config BLK_DEV_DM_BUILTIN\ndrivers/md/Kconfig-222-\tbool\ndrivers/md/Kconfig-223-\ndrivers/md/Kconfig:224:config BLK_DEV_DM\ndrivers/md/Kconfig-225-\ttristate \"Device mapper support\"\n"
}

75/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 39707
							output: 24
							thoughts: 26

Thoughts:

Here's my take on those thoughts:

**Considering Block Device Drivers and Encryption**

Okay, so I'm thinking about incorporating `BLK_DEV_DM` – Data Mapper block devices – into the system. It's a key piece for things like logical volumes, snapshots, and encryption at the block level. I'm wondering about the implications of integrating that. We need to be mindful of performance, complexity, and how it interacts with other drivers.

Then, my mind wanders to `BLK_INLINE_ENCRYPTION`. That's another vital area, especially for security-conscious deployments. I'm assessing whether to enable it, I need to understand its capabilities. I should explore its advantages versus other encryption options, and how it might impact the existing block device stack. Also I need to identify any potential conflicts between these two drivers. What about performance characteristics, too? I'm already thinking about potential optimization strategies depending on the platform.

76/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config BLK_INLINE_ENCRYPTION"
}

Results:

{
  "Output": "block/Kconfig=185=config BLK_SED_OPAL\n--\nblock/Kconfig-194-\nblock/Kconfig:195:config BLK_INLINE_ENCRYPTION\nblock/Kconfig-196-\tbool \"Enable inline encryption support in block layer\"\n--\nblock/Kconfig-201-\nblock/Kconfig:202:config BLK_INLINE_ENCRYPTION_FALLBACK\nblock/Kconfig-203-\tbool \"Enable crypto API fallback for blk-crypto\"\n"
}

77/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 40096
							output: 20
							thoughts: 39

Thoughts:

Okay, here's my take on those thoughts, tailored for an expert audience:

**Adding Encryption and Considering Filesystem Compatibility**

Alright, I'm thinking we need to introduce `BLK_INLINE_ENCRYPTION` and its fallback, `BLK_INLINE_ENCRYPTION_FALLBACK`. This seems like a natural progression, given the current discussion on enhancing security at the block level. We know we have users requesting this.

My immediate next step, and it's a critical one, is to verify the interaction with `GFS2_FS`. I've got to ensure there's no inherent conflict or incompatibility there. We can't just slap this in without a thorough look at the filesystem's behavior. We know how sensitive these things are.

78/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config GFS2_FS"
}

Results:

{
  "Output": "fs/gfs2/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/gfs2/Kconfig:2:config GFS2_FS\nfs/gfs2/Kconfig-3-\ttristate \"GFS2 file system support\"\n--\nfs/gfs2/Kconfig-26-\nfs/gfs2/Kconfig:27:config GFS2_FS_LOCKING_DLM\nfs/gfs2/Kconfig-28-\tbool \"GFS2 DLM locking\"\n"
}

79/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 40457
							output: 22
							thoughts: 23

Thoughts:

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Adding a Filesystem and a Persistent Memory Device Consideration**

Alright, the objective is to introduce a new filesystem, let's call it `GFS2_FS`. Fine, I'm noting that; it's a worthwhile addition. But before I get too deep into the implications of this, I need to consider all the pieces that are going to be affected, and how it will interact with existing systems.

Now, hold on. Before I dive into `GFS2_FS`, I should probably also check the status of `BLK_DEV_PMEM`. Persistent memory devices are becoming more prevalent, and the interactions between filesystems and these memory technologies are complex and important. If these two things are going to interact, I'm going to want to make sure the interactions between them are clearly defined.

I need to make sure I understand the full scope of how these things will integrate before making any architectural decisions.

80/2

2026/08/04 07:22

tool

grepper

Args:

{
  "Expression": "config BLK_DEV_PMEM"
}

Results:

{
  "Output": "drivers/nvdimm/Kconfig=17=if LIBNVDIMM\ndrivers/nvdimm/Kconfig-18-\ndrivers/nvdimm/Kconfig:19:config BLK_DEV_PMEM\ndrivers/nvdimm/Kconfig-20-\ttristate \"PMEM: Persistent memory block device support\"\n"
}

81/2

2026/08/04 07:22

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 40804
							output: 21
							thoughts: 25

Thoughts:

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Considering Persistent Memory Device Support**

Alright, the core work we're doing now revolves around persistent memory devices, specifically integrating them into the block layer. First thing on the docket, and probably the most crucial, is adding that `BLK_DEV_PMEM` define. This is the keystone, defining our support within the block layer itself. It's the flag we'll use to identify persistent memory devices within the core infrastructure. I need to make sure this is added correctly, that it aligns with our existing conventions, and doesn't introduce any conflicts with existing flags.

Then, immediately following that, it's essential to confirm that our `VIRTIO_PMEM` driver setup is working. We need to assess how it works with the block layer; we want to ensure everything behaves as it should. We need to make sure we've properly hooked it up to leverage the persistent memory. I need to review the existing implementation and ensure it correctly handles the nuances of a persistent memory device within a virtualized environment, and confirm it leverages any new `BLK_DEV_PMEM` hooks.

82/2

2026/08/04 07:23

tool

grepper

Args:

{
  "Expression": "config VIRTIO_PMEM"
}

Results:

{
  "Output": "drivers/virtio/Kconfig=88=config VIRTIO_VDPA\n--\ndrivers/virtio/Kconfig-100-\ndrivers/virtio/Kconfig:101:config VIRTIO_PMEM\ndrivers/virtio/Kconfig-102-\ttristate \"Support for virtio pmem driver\"\n"
}

83/2

2026/08/04 07:23

llm

patch-evaluator

Model:

gemini-3.1-pro-preview

Args:

null

Results:

null

Tokens:

							input: 41193
							output: 492
							thoughts: 651

Thoughts:

**Analyzing Block Layer Cgroup Association Changes**

Okay, let's add `VIRTIO_PMEM`. Now, let's dive into these configurations to ensure everything's properly enabled: `BLK_CGROUP`, `BLK_CGROUP_IOLATENCY`, `BLK_CGROUP_IOCOST`, `BLK_CGROUP_IOPRIO`, `IOSCHED_BFQ`, `BFQ_GROUP_IOSCHED`, `NVME_FC`, `BLK_CGROUP_FC_APPID`, `BTRFS_FS`, `MEMCG`, `BLK_DEV_THROTTLING`, `BLK_DEV_MD`, `BCACHE`, `BLK_DEV_DM`, `BLK_INLINE_ENCRYPTION`, `BLK_INLINE_ENCRYPTION_FALLBACK`, `GFS2_FS`, `BLK_DEV_PMEM`, and of course, `VIRTIO_PMEM` again. This is a pretty exhaustive list; it should cover all the code paths modified by the patch.

Next, I need to understand the functional implications. Let's look at the key symbols: `bio_blkg_lookup`, `bio_blkg`, `bio_associate_blkcg_from_css`, `bio_associate_blkcg`, `bio_clone_blkcg_association`, `bio_put_blkg_ref`, `blkcg_punt_bio_submit`, `bfq_bio_bfqg`, `blkcg_get_fc_appid`, `blkcg_set_ioprio`, `__blk_throtl_bio`, `bfqg_stats_update_legacy_io`, and `blk_cgroup_bio_start`. These are all the non-static functions this patch touches or introduces, and are highly relevant to what's changed.

From what I can gather, this patch represents a core refactoring of the block layer's cgroup association logic. It's fundamentally changing how a `bio` is linked with a `blkcg` and `blkg`. The old `bio->bi_blkg` pointer is being replaced. New functions like `bio_blkg_lookup` and `bio_blkg` are introduced for lookup and pinning. This affects a whole host of subsystems: BFQ, iocost, iolatency, ioprio, throttle, bcache, dm, md, nvdimm, gfs2, and btrfs are all being updated to use this new API. Considering this touches the core block layer, and is reachable in virtualized environments, this is definitely a critical functional change that's prime for fuzzing. We need to validate this deeply.

Alright, let's call the `set-results` tool now.

84/2

2026/08/04 07:23

tool

set-results

Args:

{
  "EnableConfigs": [
    "BLK_CGROUP",
    "BLK_CGROUP_IOLATENCY",
    "BLK_CGROUP_IOCOST",
    "BLK_CGROUP_IOPRIO",
    "IOSCHED_BFQ",
    "BFQ_GROUP_IOSCHED",
    "NVME_FC",
    "BLK_CGROUP_FC_APPID",
    "BTRFS_FS",
    "MEMCG",
    "BLK_DEV_THROTTLING",
    "BLK_DEV_MD",
    "BCACHE",
    "BLK_DEV_DM",
    "BLK_INLINE_ENCRYPTION",
    "BLK_INLINE_ENCRYPTION_FALLBACK",
    "GFS2_FS",
    "BLK_DEV_PMEM",
    "VIRTIO_PMEM"
  ],
  "FocusSymbols": [
    "bio_blkg_lookup",
    "bio_blkg",
    "bio_associate_blkcg_from_css",
    "bio_associate_blkcg",
    "bio_clone_blkcg_association",
    "bio_put_blkg_ref",
    "blkcg_punt_bio_submit",
    "bfq_bio_bfqg",
    "blkcg_get_fc_appid",
    "blkcg_set_ioprio",
    "__blk_throtl_bio",
    "bfqg_stats_update_legacy_io",
    "blk_cgroup_bio_start"
  ],
  "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.",
  "WorthFuzzing": true
}

Results:

{
  "EnableConfigs": [
    "BLK_CGROUP",
    "BLK_CGROUP_IOLATENCY",
    "BLK_CGROUP_IOCOST",
    "BLK_CGROUP_IOPRIO",
    "IOSCHED_BFQ",
    "BFQ_GROUP_IOSCHED",
    "NVME_FC",
    "BLK_CGROUP_FC_APPID",
    "BTRFS_FS",
    "MEMCG",
    "BLK_DEV_THROTTLING",
    "BLK_DEV_MD",
    "BCACHE",
    "BLK_DEV_DM",
    "BLK_INLINE_ENCRYPTION",
    "BLK_INLINE_ENCRYPTION_FALLBACK",
    "GFS2_FS",
    "BLK_DEV_PMEM",
    "VIRTIO_PMEM"
  ],
  "FocusSymbols": [
    "bio_blkg_lookup",
    "bio_blkg",
    "bio_associate_blkcg_from_css",
    "bio_associate_blkcg",
    "bio_clone_blkcg_association",
    "bio_put_blkg_ref",
    "blkcg_punt_bio_submit",
    "bfq_bio_bfqg",
    "blkcg_get_fc_appid",
    "blkcg_set_ioprio",
    "__blk_throtl_bio",
    "bfqg_stats_update_legacy_io",
    "blk_cgroup_bio_start"
  ],
  "Reasoning": "The patch refactors how `bio` structures are associated with block cgroups (`blkcg` and `blkg`). It replaces the direct `bio-\u003ebi_blkg` pointer with `bio-\u003ebi_blkcg` and introduces new lookup and pinning functions (`bio_blkg_lookup`, `bio_blkg`). It updates multiple block layer subsystems (BFQ, iocost, iolatency, ioprio, throttle), drivers (bcache, dm, md, nvdimm), and filesystems (btrfs, gfs2) to use the new API. This is a significant functional change in core kernel logic that is reachable in virtualized environments and should be fuzzed.",
  "WorthFuzzing": true
}