AI Trajectory


Trajectory: (Expand/Collapse All)
Seq Timestamp Type Name Duration
0/0 2026/07/23 21:33 flow patch-triage
1m Args: 
null

Results: 
{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA",
    "NVME_TARGET"
  ],
  "FocusSymbols": [
    "raid1_write_error",
    "narrow_write_error",
    "handle_write_finished",
    "handle_write_completed",
    "handle_read_error",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch introduces handling for BLK_STS_P2PDMA errors in the block layer, MD RAID (RAID1/RAID10), and NVMe RDMA. It modifies error handling paths in MD RAID to properly handle P2PDMA mapping failures by setting badblocks or blocking reads instead of failing the underlying device. It also modifies NVMe RDMA to use ib_dma_map_sgtable_attrs and return BLK_STS_P2PDMA on mapping failures. These changes are functionally reachable in virtualized environments by configuring NVMe targets with P2P memory backed by MD arrays, or by using NVMe RDMA over software RDMA devices.",
  "WorthFuzzing": true
}
1/1 2026/07/23 21:33 action read-patch-diff
0m Args: 
null

Results: 
{
  "PatchDiff": "commit 371ed603ebd7a68376bb820ef8de07acbf7355de\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Jul 23 21:33:07 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/block/blk-core.c b/block/blk-core.c\nindex 365641266c9e82..83cb5464265fb6 100644\n--- a/block/blk-core.c\n+++ b/block/blk-core.c\n@@ -177,6 +177,9 @@ static const struct {\n \n \t/* Command duration limit device-side timeout */\n \tENT(DURATION_LIMIT,\t-ETIME,\t\t\"duration limit exceeded\"),\n+\n+\t/* no PCIe P2PDMA route between initiator and target */\n+\tENT(P2PDMA,\t\t-EREMOTEIO,\t\"peer-to-peer transfer unroutable\"),\n \tENT(INVAL,\t\t-EINVAL,\t\"invalid\"),\n \n \t/* everything else not covered above: */\ndiff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c\nindex bfdb9ed7074116..e88d6b3524e6ad 100644\n--- a/block/blk-mq-dma.c\n+++ b/block/blk-mq-dma.c\n@@ -189,8 +189,9 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,\n \t\t */\n \tcase PCI_P2PDMA_MAP_NONE:\n \t\tbreak;\n+\tcase PCI_P2PDMA_MAP_NOT_SUPPORTED:\n \tdefault:\n-\t\titer-\u003estatus = BLK_STS_INVAL;\n+\t\titer-\u003estatus = BLK_STS_P2PDMA;\n \t\treturn false;\n \t}\n \ndiff --git a/drivers/md/md.c b/drivers/md/md.c\nindex d1465bcd86c812..3770bdb4d4b28b 100644\n--- a/drivers/md/md.c\n+++ b/drivers/md/md.c\n@@ -451,8 +451,14 @@ static void md_submit_bio(struct bio *bio)\n \t\treturn;\n \t}\n \n-\t/* bio could be mergeable after passing to underlayer */\n-\tbio-\u003ebi_opf \u0026= ~REQ_NOMERGE;\n+\t/*\n+\t * A bio md split may merge again below md -- except P2PDMA bios,\n+\t * which must stay single-provider (see __bio_add_page()).\n+\t */\n+\tif (md_bio_is_p2pdma(bio))\n+\t\tbio-\u003ebi_opf |= REQ_NOMERGE;\n+\telse\n+\t\tbio-\u003ebi_opf \u0026= ~REQ_NOMERGE;\n \n \tmd_handle_request(mddev, bio);\n }\ndiff --git a/drivers/md/md.h b/drivers/md/md.h\nindex d8daf0f75cbbe8..73df1a6eccd850 100644\n--- a/drivers/md/md.h\n+++ b/drivers/md/md.h\n@@ -11,8 +11,10 @@\n #include \u003clinux/blkdev.h\u003e\n #include \u003clinux/backing-dev.h\u003e\n #include \u003clinux/badblocks.h\u003e\n+#include \u003clinux/bio.h\u003e\n #include \u003clinux/kobject.h\u003e\n #include \u003clinux/list.h\u003e\n+#include \u003clinux/memremap.h\u003e\n #include \u003clinux/mm.h\u003e\n #include \u003clinux/mutex.h\u003e\n #include \u003clinux/timer.h\u003e\n@@ -22,6 +24,19 @@\n #include \u003ctrace/events/block.h\u003e\n \n #define MaxSector (~(sector_t)0)\n+\n+/*\n+ * P2P and host pages never mix within a bio, so the first bvec is\n+ * representative.  Read bi_io_vec directly: bio_first_bvec_all()\n+ * WARNs on the split clones md handles, and data-less bios have no\n+ * bi_io_vec.  Not valid after the bio's iterator is consumed.\n+ */\n+static inline bool md_bio_is_p2pdma(struct bio *bio)\n+{\n+\treturn bio_has_data(bio) \u0026\u0026 bio-\u003ebi_io_vec \u0026\u0026\n+\t       is_pci_p2pdma_page(bio-\u003ebi_io_vec-\u003ebv_page);\n+}\n+\n /*\n  * Number of guaranteed raid bios in case of extreme VM load:\n  */\ndiff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c\nindex 56a56a4da4f83f..89daf8558251fa 100644\n--- a/drivers/md/raid1-10.c\n+++ b/drivers/md/raid1-10.c\n@@ -303,3 +303,19 @@ static inline bool raid1_should_handle_error(struct bio *bio)\n \treturn !(bio-\u003ebi_opf \u0026 (REQ_RAHEAD | REQ_NOWAIT)) \u0026\u0026\n \t\tbio-\u003ebi_status != BLK_STS_INVAL;\n }\n+\n+static inline void raid1_write_error(struct mddev *mddev, struct md_rdev *rdev,\n+\t\t\t\t     struct bio *bio, bool allow_failfast)\n+{\n+\tset_bit(WriteErrorSeen, \u0026rdev-\u003eflags);\n+\n+\tif (bio-\u003ebi_status == BLK_STS_P2PDMA)\n+\t\treturn;\n+\n+\tif (!test_and_set_bit(WantReplacement, \u0026rdev-\u003eflags))\n+\t\tset_bit(MD_RECOVERY_NEEDED, \u0026mddev-\u003erecovery);\n+\n+\tif (allow_failfast \u0026\u0026 test_bit(FailFast, \u0026rdev-\u003eflags) \u0026\u0026\n+\t    (bio-\u003ebi_opf \u0026 MD_FAILFAST))\n+\t\tmd_error(mddev, rdev);\n+}\ndiff --git a/drivers/md/raid1.c b/drivers/md/raid1.c\nindex afe2ca96ad8c22..76a1426e64f02d 100644\n--- a/drivers/md/raid1.c\n+++ b/drivers/md/raid1.c\n@@ -483,17 +483,8 @@ static void raid1_end_write_request(struct bio *bio)\n \t * 'one mirror IO has finished' event handler:\n \t */\n \tif (bio-\u003ebi_status \u0026\u0026 !ignore_error) {\n-\t\tset_bit(WriteErrorSeen,\t\u0026rdev-\u003eflags);\n-\t\tif (!test_and_set_bit(WantReplacement, \u0026rdev-\u003eflags))\n-\t\t\tset_bit(MD_RECOVERY_NEEDED, \u0026\n-\t\t\t\tconf-\u003emddev-\u003erecovery);\n-\n-\t\tif (test_bit(FailFast, \u0026rdev-\u003eflags) \u0026\u0026\n-\t\t    (bio-\u003ebi_opf \u0026 MD_FAILFAST) \u0026\u0026\n-\t\t    /* We never try FailFast to WriteMostly devices */\n-\t\t    !test_bit(WriteMostly, \u0026rdev-\u003eflags)) {\n-\t\t\tmd_error(r1_bio-\u003emddev, rdev);\n-\t\t}\n+\t\traid1_write_error(conf-\u003emddev, rdev, bio,\n+\t\t\t\t  !test_bit(WriteMostly, \u0026rdev-\u003eflags));\n \n \t\t/*\n \t\t * When the device is faulty, it is not necessary to\n@@ -564,7 +555,7 @@ static void raid1_end_write_request(struct bio *bio)\n \t\t\t\tcall_bio_endio(r1_bio);\n \t\t\t}\n \t\t}\n-\t} else if (test_bit(MD_SERIALIZE_POLICY, \u0026rdev-\u003emddev-\u003eflags))\n+\t} else if (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\n \t\tremove_serial(rdev, lo, hi);\n \tif (r1_bio-\u003ebios[mirror] == NULL)\n \t\trdev_dec_pending(rdev, conf-\u003emddev);\n@@ -1523,6 +1514,7 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,\n \tbool write_behind = false;\n \tbool nowait = bio-\u003ebi_opf \u0026 REQ_NOWAIT;\n \tbool is_discard = op_is_discard(bio-\u003ebi_opf);\n+\tbool is_p2pdma = md_bio_is_p2pdma(bio);\n \tsector_t sector = bio-\u003ebi_iter.bi_sector;\n \n \tif (mddev_is_clustered(mddev) \u0026\u0026\n@@ -1575,9 +1567,12 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,\n \t\t/*\n \t\t * The write-behind io is only attempted on drives marked as\n \t\t * write-mostly, which means we could allocate write behind\n-\t\t * bio later.\n+\t\t * bio later. P2PDMA bios are excluded: write-behind copies\n+\t\t * the data with bio_copy_data(), a CPU copy that cannot be\n+\t\t * assumed safe or fast on P2PDMA (device BAR) pages.\n \t\t */\n-\t\tif (!is_discard \u0026\u0026 rdev \u0026\u0026 test_bit(WriteMostly, \u0026rdev-\u003eflags))\n+\t\tif (!is_discard \u0026\u0026 !is_p2pdma \u0026\u0026 rdev \u0026\u0026\n+\t\t    test_bit(WriteMostly, \u0026rdev-\u003eflags))\n \t\t\twrite_behind = true;\n \n \t\tr1_bio-\u003ebios[i] = NULL;\n@@ -1677,7 +1672,11 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,\n \t\t\tmbio = bio_alloc_clone(rdev-\u003ebdev, bio, GFP_NOIO,\n \t\t\t\t\t       \u0026mddev-\u003ebio_set);\n \n-\t\t\tif (test_bit(MD_SERIALIZE_POLICY, \u0026mddev-\u003eflags))\n+\t\t\t/*\n+\t\t\t * CollisionCheck marks every rdev with a serial\n+\t\t\t * tree; order against in-flight write-behind I/O.\n+\t\t\t */\n+\t\t\tif (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\n \t\t\t\twait_for_serialization(rdev, r1_bio);\n \t\t}\n \n@@ -2562,6 +2561,9 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)\n \t\t}\n \n \t\twbio-\u003ebi_opf = REQ_OP_WRITE;\n+\t\t/* Keep P2PDMA retry bios unmergeable, like the original */\n+\t\tif (md_bio_is_p2pdma(wbio))\n+\t\t\twbio-\u003ebi_opf |= REQ_NOMERGE;\n \t\twbio-\u003ebi_iter.bi_sector = r1_bio-\u003esector;\n \t\twbio-\u003ebi_iter.bi_size = r1_bio-\u003esectors \u003c\u003c 9;\n \n@@ -2622,10 +2624,16 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)\n \t\t\t * narrow down and record precise write\n \t\t\t * errors.\n \t\t\t */\n+\t\t\tstruct md_rdev *rdev = conf-\u003emirrors[m].rdev;\n+\n \t\t\tfail = true;\n-\t\t\tnarrow_write_error(r1_bio, m);\n-\t\t\trdev_dec_pending(conf-\u003emirrors[m].rdev,\n-\t\t\t\t\t conf-\u003emddev);\n+\t\t\t/* Mapping failures are whole-range and deterministic */\n+\t\t\tif (r1_bio-\u003ebios[m]-\u003ebi_status == BLK_STS_P2PDMA)\n+\t\t\t\trdev_set_badblocks(rdev, r1_bio-\u003esector,\n+\t\t\t\t\t\t   r1_bio-\u003esectors, 0);\n+\t\t\telse\n+\t\t\t\tnarrow_write_error(r1_bio, m);\n+\t\t\trdev_dec_pending(rdev, conf-\u003emddev);\n \t\t}\n \tif (fail) {\n \t\tspin_lock_irq(\u0026conf-\u003edevice_lock);\n@@ -2650,6 +2658,8 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n {\n \tstruct md_rdev *rdev = conf-\u003emirrors[r1_bio-\u003eread_disk].rdev;\n \tstruct bio *bio = r1_bio-\u003ebios[r1_bio-\u003eread_disk];\n+\t/* evaluate before the bio_put() below */\n+\tbool p2pdma_error = bio-\u003ebi_status == BLK_STS_P2PDMA;\n \tstruct mddev *mddev = conf-\u003emddev;\n \tsector_t sector;\n \n@@ -2667,7 +2677,7 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n \t * read error.  This is all done synchronously while the array is\n \t * frozen.\n \t */\n-\tif (mddev-\u003ero) {\n+\tif (mddev-\u003ero || p2pdma_error) {\n \t\tr1_bio-\u003ebios[r1_bio-\u003eread_disk] = IO_BLOCKED;\n \t} else if (test_bit(FailFast, \u0026rdev-\u003eflags)) {\n \t\tmd_error(mddev, rdev);\ndiff --git a/drivers/md/raid10.c b/drivers/md/raid10.c\nindex 0a3cfdd3f5df80..e35aeac29f0642 100644\n--- a/drivers/md/raid10.c\n+++ b/drivers/md/raid10.c\n@@ -482,16 +482,8 @@ static void raid10_end_write_request(struct bio *bio)\n \t\t\t */\n \t\t\tmd_error(rdev-\u003emddev, rdev);\n \t\telse {\n-\t\t\tset_bit(WriteErrorSeen,\t\u0026rdev-\u003eflags);\n-\t\t\tif (!test_and_set_bit(WantReplacement, \u0026rdev-\u003eflags))\n-\t\t\t\tset_bit(MD_RECOVERY_NEEDED,\n-\t\t\t\t\t\u0026rdev-\u003emddev-\u003erecovery);\n-\n \t\t\tdec_rdev = 0;\n-\t\t\tif (test_bit(FailFast, \u0026rdev-\u003eflags) \u0026\u0026\n-\t\t\t    (bio-\u003ebi_opf \u0026 MD_FAILFAST)) {\n-\t\t\t\tmd_error(rdev-\u003emddev, rdev);\n-\t\t\t}\n+\t\t\traid1_write_error(rdev-\u003emddev, rdev, bio, true);\n \n \t\t\t/*\n \t\t\t * When the device is faulty, it is not necessary to\n@@ -2831,6 +2823,9 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)\n \t\twbio-\u003ebi_iter.bi_sector = wsector +\n \t\t\t\t   choose_data_offset(r10_bio, rdev);\n \t\twbio-\u003ebi_opf = REQ_OP_WRITE;\n+\t\t/* Keep P2PDMA retry bios unmergeable, like the original */\n+\t\tif (md_bio_is_p2pdma(wbio))\n+\t\t\twbio-\u003ebi_opf |= REQ_NOMERGE;\n \n \t\tif (submit_bio_wait(wbio) \u0026\u0026\n \t\t    !rdev_set_badblocks(rdev, wsector, sectors, 0)) {\n@@ -2853,6 +2848,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)\n {\n \tint slot = r10_bio-\u003eread_slot;\n \tstruct bio *bio;\n+\tbool p2pdma_error;\n \tstruct r10conf *conf = mddev-\u003eprivate;\n \tstruct md_rdev *rdev = r10_bio-\u003edevs[slot].rdev;\n \n@@ -2865,10 +2861,12 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)\n \t * frozen.\n \t */\n \tbio = r10_bio-\u003edevs[slot].bio;\n+\t/* evaluate before the bio_put() below */\n+\tp2pdma_error = bio-\u003ebi_status == BLK_STS_P2PDMA;\n \tbio_put(bio);\n \tr10_bio-\u003edevs[slot].bio = NULL;\n \n-\tif (mddev-\u003ero)\n+\tif (mddev-\u003ero || p2pdma_error)\n \t\tr10_bio-\u003edevs[slot].bio = IO_BLOCKED;\n \telse if (!test_bit(FailFast, \u0026rdev-\u003eflags)) {\n \t\tfreeze_array(conf, 1);\n@@ -2945,7 +2943,13 @@ static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)\n \t\t\t\trdev_dec_pending(rdev, conf-\u003emddev);\n \t\t\t} else if (bio != NULL \u0026\u0026 bio-\u003ebi_status) {\n \t\t\t\tfail = true;\n-\t\t\t\tnarrow_write_error(r10_bio, m);\n+\t\t\t\t/* Mapping failures are whole-range and deterministic */\n+\t\t\t\tif (bio-\u003ebi_status == BLK_STS_P2PDMA)\n+\t\t\t\t\trdev_set_badblocks(rdev,\n+\t\t\t\t\t\t\t   r10_bio-\u003edevs[m].addr,\n+\t\t\t\t\t\t\t   r10_bio-\u003esectors, 0);\n+\t\t\t\telse\n+\t\t\t\t\tnarrow_write_error(r10_bio, m);\n \t\t\t\trdev_dec_pending(rdev, conf-\u003emddev);\n \t\t\t}\n \t\t\tbio = r10_bio-\u003edevs[m].repl_bio;\ndiff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c\nindex 6909e354279427..2f50509a7a6160 100644\n--- a/drivers/nvme/host/rdma.c\n+++ b/drivers/nvme/host/rdma.c\n@@ -1469,6 +1469,7 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,\n \t\tint *count, int *pi_count)\n {\n \tstruct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);\n+\tstruct sg_table sgt;\n \tint ret;\n \n \treq-\u003edata_sgl.sg_table.sgl = (struct scatterlist *)(req + 1);\n@@ -1480,12 +1481,14 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,\n \n \treq-\u003edata_sgl.nents = blk_rq_map_sg(rq, req-\u003edata_sgl.sg_table.sgl);\n \n-\t*count = ib_dma_map_sg(ibdev, req-\u003edata_sgl.sg_table.sgl,\n-\t\t\t       req-\u003edata_sgl.nents, rq_dma_dir(rq));\n-\tif (unlikely(*count \u003c= 0)) {\n-\t\tret = -EIO;\n+\tsgt = (struct sg_table) {\n+\t\t.sgl\t\t= req-\u003edata_sgl.sg_table.sgl,\n+\t\t.orig_nents\t= req-\u003edata_sgl.nents,\n+\t};\n+\tret = ib_dma_map_sgtable_attrs(ibdev, \u0026sgt, rq_dma_dir(rq), 0);\n+\tif (unlikely(ret))\n \t\tgoto out_free_table;\n-\t}\n+\t*count = sgt.nents;\n \n \tif (blk_integrity_rq(rq)) {\n \t\treq-\u003emetadata_sgl-\u003esg_table.sgl =\n@@ -1501,14 +1504,14 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,\n \n \t\treq-\u003emetadata_sgl-\u003enents = blk_rq_map_integrity_sg(rq,\n \t\t\t\treq-\u003emetadata_sgl-\u003esg_table.sgl);\n-\t\t*pi_count = ib_dma_map_sg(ibdev,\n-\t\t\t\t\t  req-\u003emetadata_sgl-\u003esg_table.sgl,\n-\t\t\t\t\t  req-\u003emetadata_sgl-\u003enents,\n-\t\t\t\t\t  rq_dma_dir(rq));\n-\t\tif (unlikely(*pi_count \u003c= 0)) {\n-\t\t\tret = -EIO;\n+\t\tsgt = (struct sg_table) {\n+\t\t\t.sgl\t\t= req-\u003emetadata_sgl-\u003esg_table.sgl,\n+\t\t\t.orig_nents\t= req-\u003emetadata_sgl-\u003enents,\n+\t\t};\n+\t\tret = ib_dma_map_sgtable_attrs(ibdev, \u0026sgt, rq_dma_dir(rq), 0);\n+\t\tif (unlikely(ret))\n \t\t\tgoto out_free_pi_table;\n-\t\t}\n+\t\t*pi_count = sgt.nents;\n \t}\n \n \treturn 0;\n@@ -2026,8 +2029,6 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,\n \tif (ret)\n \t\tgoto unmap_qe;\n \n-\tnvme_start_request(rq);\n-\n \tif (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) \u0026\u0026\n \t    queue-\u003epi_support \u0026\u0026\n \t    (c-\u003ecommon.opcode == nvme_cmd_write ||\n@@ -2039,11 +2040,13 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,\n \n \terr = nvme_rdma_map_data(queue, rq, c);\n \tif (unlikely(err \u003c 0)) {\n-\t\tdev_err(queue-\u003ectrl-\u003ectrl.device,\n-\t\t\t     \"Failed to map data (%d)\\n\", err);\n+\t\tdev_err_ratelimited(queue-\u003ectrl-\u003ectrl.device,\n+\t\t\t\t    \"Failed to map data (%d)\\n\", err);\n \t\tgoto err;\n \t}\n \n+\tnvme_start_request(rq);\n+\n \tsqe-\u003ecqe.done = nvme_rdma_send_done;\n \n \tib_dma_sync_single_for_device(dev, sqe-\u003edma,\n@@ -2063,6 +2066,9 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,\n \t\tret = nvme_host_path_error(rq);\n \telse if (err == -ENOMEM || err == -EAGAIN)\n \t\tret = BLK_STS_RESOURCE;\n+\t/* Peer memory unreachable from this device: don't retry. */\n+\telse if (err == -EREMOTEIO)\n+\t\tret = BLK_STS_P2PDMA;\n \telse\n \t\tret = BLK_STS_IOERR;\n \tnvme_cleanup_cmd(rq);\ndiff --git a/include/linux/blk_types.h b/include/linux/blk_types.h\nindex 8808ee76e73c09..c8de7809320ad4 100644\n--- a/include/linux/blk_types.h\n+++ b/include/linux/blk_types.h\n@@ -165,6 +165,15 @@ typedef u16 blk_short_t;\n  */\n #define BLK_STS_DURATION_LIMIT\t((__force blk_status_t)17)\n \n+/*\n+ * BLK_STS_P2PDMA is returned when a peer-to-peer DMA transfer cannot be\n+ * mapped (typically because there is no route between the initiator and the\n+ * target that the platform's PCIe topology and ACS settings allow). This\n+ * is a property of the initiator/target pair, not of the target device's\n+ * health. This error should never be retried.\n+ */\n+#define BLK_STS_P2PDMA\t((__force blk_status_t)18)\n+\n /*\n  * Invalid size or alignment.\n  */\n@@ -188,6 +197,7 @@ static inline bool blk_path_error(blk_status_t error)\n \tcase BLK_STS_NOTSUPP:\n \tcase BLK_STS_NOSPC:\n \tcase BLK_STS_TARGET:\n+\tcase BLK_STS_P2PDMA:\n \tcase BLK_STS_RESV_CONFLICT:\n \tcase BLK_STS_MEDIUM:\n \tcase BLK_STS_PROTECTION:\n"
}
2/1 2026/07/23 21:33 agent patch-evaluator
1m Model: 
best-expensive

Args: 
null

Results: 
{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA",
    "NVME_TARGET"
  ],
  "FocusSymbols": [
    "raid1_write_error",
    "narrow_write_error",
    "handle_write_finished",
    "handle_write_completed",
    "handle_read_error",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch introduces handling for BLK_STS_P2PDMA errors in the block layer, MD RAID (RAID1/RAID10), and NVMe RDMA. It modifies error handling paths in MD RAID to properly handle P2PDMA mapping failures by setting badblocks or blocking reads instead of failing the underlying device. It also modifies NVMe RDMA to use ib_dma_map_sgtable_attrs and return BLK_STS_P2PDMA on mapping failures. These changes are functionally reachable in virtualized environments by configuring NVMe targets with P2P memory backed by MD arrays, or by using NVMe RDMA over software RDMA devices.",
  "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).

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.
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.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. 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 371ed603ebd7a68376bb820ef8de07acbf7355de
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Jul 23 21:33:07 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/blk-core.c b/block/blk-core.c
index 365641266c9e82..83cb5464265fb6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -177,6 +177,9 @@ static const struct {
 
 	/* Command duration limit device-side timeout */
 	ENT(DURATION_LIMIT,	-ETIME,		"duration limit exceeded"),
+
+	/* no PCIe P2PDMA route between initiator and target */
+	ENT(P2PDMA,		-EREMOTEIO,	"peer-to-peer transfer unroutable"),
 	ENT(INVAL,		-EINVAL,	"invalid"),
 
 	/* everything else not covered above: */
diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index bfdb9ed7074116..e88d6b3524e6ad 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -189,8 +189,9 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,
 		 */
 	case PCI_P2PDMA_MAP_NONE:
 		break;
+	case PCI_P2PDMA_MAP_NOT_SUPPORTED:
 	default:
-		iter->status = BLK_STS_INVAL;
+		iter->status = BLK_STS_P2PDMA;
 		return false;
 	}
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d1465bcd86c812..3770bdb4d4b28b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -451,8 +451,14 @@ static void md_submit_bio(struct bio *bio)
 		return;
 	}
 
-	/* bio could be mergeable after passing to underlayer */
-	bio->bi_opf &= ~REQ_NOMERGE;
+	/*
+	 * A bio md split may merge again below md -- except P2PDMA bios,
+	 * which must stay single-provider (see __bio_add_page()).
+	 */
+	if (md_bio_is_p2pdma(bio))
+		bio->bi_opf |= REQ_NOMERGE;
+	else
+		bio->bi_opf &= ~REQ_NOMERGE;
 
 	md_handle_request(mddev, bio);
 }
diff --git a/drivers/md/md.h b/drivers/md/md.h
index d8daf0f75cbbe8..73df1a6eccd850 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -11,8 +11,10 @@
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/badblocks.h>
+#include <linux/bio.h>
 #include <linux/kobject.h>
 #include <linux/list.h>
+#include <linux/memremap.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/timer.h>
@@ -22,6 +24,19 @@
 #include <trace/events/block.h>
 
 #define MaxSector (~(sector_t)0)
+
+/*
+ * P2P and host pages never mix within a bio, so the first bvec is
+ * representative.  Read bi_io_vec directly: bio_first_bvec_all()
+ * WARNs on the split clones md handles, and data-less bios have no
+ * bi_io_vec.  Not valid after the bio's iterator is consumed.
+ */
+static inline bool md_bio_is_p2pdma(struct bio *bio)
+{
+	return bio_has_data(bio) && bio->bi_io_vec &&
+	       is_pci_p2pdma_page(bio->bi_io_vec->bv_page);
+}
+
 /*
  * Number of guaranteed raid bios in case of extreme VM load:
  */
diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
index 56a56a4da4f83f..89daf8558251fa 100644
--- a/drivers/md/raid1-10.c
+++ b/drivers/md/raid1-10.c
@@ -303,3 +303,19 @@ static inline bool raid1_should_handle_error(struct bio *bio)
 	return !(bio->bi_opf & (REQ_RAHEAD | REQ_NOWAIT)) &&
 		bio->bi_status != BLK_STS_INVAL;
 }
+
+static inline void raid1_write_error(struct mddev *mddev, struct md_rdev *rdev,
+				     struct bio *bio, bool allow_failfast)
+{
+	set_bit(WriteErrorSeen, &rdev->flags);
+
+	if (bio->bi_status == BLK_STS_P2PDMA)
+		return;
+
+	if (!test_and_set_bit(WantReplacement, &rdev->flags))
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+
+	if (allow_failfast && test_bit(FailFast, &rdev->flags) &&
+	    (bio->bi_opf & MD_FAILFAST))
+		md_error(mddev, rdev);
+}
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index afe2ca96ad8c22..76a1426e64f02d 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -483,17 +483,8 @@ static void raid1_end_write_request(struct bio *bio)
 	 * 'one mirror IO has finished' event handler:
 	 */
 	if (bio->bi_status && !ignore_error) {
-		set_bit(WriteErrorSeen,	&rdev->flags);
-		if (!test_and_set_bit(WantReplacement, &rdev->flags))
-			set_bit(MD_RECOVERY_NEEDED, &
-				conf->mddev->recovery);
-
-		if (test_bit(FailFast, &rdev->flags) &&
-		    (bio->bi_opf & MD_FAILFAST) &&
-		    /* We never try FailFast to WriteMostly devices */
-		    !test_bit(WriteMostly, &rdev->flags)) {
-			md_error(r1_bio->mddev, rdev);
-		}
+		raid1_write_error(conf->mddev, rdev, bio,
+				  !test_bit(WriteMostly, &rdev->flags));
 
 		/*
 		 * When the device is faulty, it is not necessary to
@@ -564,7 +555,7 @@ static void raid1_end_write_request(struct bio *bio)
 				call_bio_endio(r1_bio);
 			}
 		}
-	} else if (test_bit(MD_SERIALIZE_POLICY, &rdev->mddev->flags))
+	} else if (test_bit(CollisionCheck, &rdev->flags))
 		remove_serial(rdev, lo, hi);
 	if (r1_bio->bios[mirror] == NULL)
 		rdev_dec_pending(rdev, conf->mddev);
@@ -1523,6 +1514,7 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,
 	bool write_behind = false;
 	bool nowait = bio->bi_opf & REQ_NOWAIT;
 	bool is_discard = op_is_discard(bio->bi_opf);
+	bool is_p2pdma = md_bio_is_p2pdma(bio);
 	sector_t sector = bio->bi_iter.bi_sector;
 
 	if (mddev_is_clustered(mddev) &&
@@ -1575,9 +1567,12 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,
 		/*
 		 * The write-behind io is only attempted on drives marked as
 		 * write-mostly, which means we could allocate write behind
-		 * bio later.
+		 * bio later. P2PDMA bios are excluded: write-behind copies
+		 * the data with bio_copy_data(), a CPU copy that cannot be
+		 * assumed safe or fast on P2PDMA (device BAR) pages.
 		 */
-		if (!is_discard && rdev && test_bit(WriteMostly, &rdev->flags))
+		if (!is_discard && !is_p2pdma && rdev &&
+		    test_bit(WriteMostly, &rdev->flags))
 			write_behind = true;
 
 		r1_bio->bios[i] = NULL;
@@ -1677,7 +1672,11 @@ static bool raid1_write_request(struct mddev *mddev, struct bio *bio,
 			mbio = bio_alloc_clone(rdev->bdev, bio, GFP_NOIO,
 					       &mddev->bio_set);
 
-			if (test_bit(MD_SERIALIZE_POLICY, &mddev->flags))
+			/*
+			 * CollisionCheck marks every rdev with a serial
+			 * tree; order against in-flight write-behind I/O.
+			 */
+			if (test_bit(CollisionCheck, &rdev->flags))
 				wait_for_serialization(rdev, r1_bio);
 		}
 
@@ -2562,6 +2561,9 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)
 		}
 
 		wbio->bi_opf = REQ_OP_WRITE;
+		/* Keep P2PDMA retry bios unmergeable, like the original */
+		if (md_bio_is_p2pdma(wbio))
+			wbio->bi_opf |= REQ_NOMERGE;
 		wbio->bi_iter.bi_sector = r1_bio->sector;
 		wbio->bi_iter.bi_size = r1_bio->sectors << 9;
 
@@ -2622,10 +2624,16 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
 			 * narrow down and record precise write
 			 * errors.
 			 */
+			struct md_rdev *rdev = conf->mirrors[m].rdev;
+
 			fail = true;
-			narrow_write_error(r1_bio, m);
-			rdev_dec_pending(conf->mirrors[m].rdev,
-					 conf->mddev);
+			/* Mapping failures are whole-range and deterministic */
+			if (r1_bio->bios[m]->bi_status == BLK_STS_P2PDMA)
+				rdev_set_badblocks(rdev, r1_bio->sector,
+						   r1_bio->sectors, 0);
+			else
+				narrow_write_error(r1_bio, m);
+			rdev_dec_pending(rdev, conf->mddev);
 		}
 	if (fail) {
 		spin_lock_irq(&conf->device_lock);
@@ -2650,6 +2658,8 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 {
 	struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;
 	struct bio *bio = r1_bio->bios[r1_bio->read_disk];
+	/* evaluate before the bio_put() below */
+	bool p2pdma_error = bio->bi_status == BLK_STS_P2PDMA;
 	struct mddev *mddev = conf->mddev;
 	sector_t sector;
 
@@ -2667,7 +2677,7 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 	 * read error.  This is all done synchronously while the array is
 	 * frozen.
 	 */
-	if (mddev->ro) {
+	if (mddev->ro || p2pdma_error) {
 		r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;
 	} else if (test_bit(FailFast, &rdev->flags)) {
 		md_error(mddev, rdev);
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0a3cfdd3f5df80..e35aeac29f0642 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -482,16 +482,8 @@ static void raid10_end_write_request(struct bio *bio)
 			 */
 			md_error(rdev->mddev, rdev);
 		else {
-			set_bit(WriteErrorSeen,	&rdev->flags);
-			if (!test_and_set_bit(WantReplacement, &rdev->flags))
-				set_bit(MD_RECOVERY_NEEDED,
-					&rdev->mddev->recovery);
-
 			dec_rdev = 0;
-			if (test_bit(FailFast, &rdev->flags) &&
-			    (bio->bi_opf & MD_FAILFAST)) {
-				md_error(rdev->mddev, rdev);
-			}
+			raid1_write_error(rdev->mddev, rdev, bio, true);
 
 			/*
 			 * When the device is faulty, it is not necessary to
@@ -2831,6 +2823,9 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)
 		wbio->bi_iter.bi_sector = wsector +
 				   choose_data_offset(r10_bio, rdev);
 		wbio->bi_opf = REQ_OP_WRITE;
+		/* Keep P2PDMA retry bios unmergeable, like the original */
+		if (md_bio_is_p2pdma(wbio))
+			wbio->bi_opf |= REQ_NOMERGE;
 
 		if (submit_bio_wait(wbio) &&
 		    !rdev_set_badblocks(rdev, wsector, sectors, 0)) {
@@ -2853,6 +2848,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 {
 	int slot = r10_bio->read_slot;
 	struct bio *bio;
+	bool p2pdma_error;
 	struct r10conf *conf = mddev->private;
 	struct md_rdev *rdev = r10_bio->devs[slot].rdev;
 
@@ -2865,10 +2861,12 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 	 * frozen.
 	 */
 	bio = r10_bio->devs[slot].bio;
+	/* evaluate before the bio_put() below */
+	p2pdma_error = bio->bi_status == BLK_STS_P2PDMA;
 	bio_put(bio);
 	r10_bio->devs[slot].bio = NULL;
 
-	if (mddev->ro)
+	if (mddev->ro || p2pdma_error)
 		r10_bio->devs[slot].bio = IO_BLOCKED;
 	else if (!test_bit(FailFast, &rdev->flags)) {
 		freeze_array(conf, 1);
@@ -2945,7 +2943,13 @@ static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
 				rdev_dec_pending(rdev, conf->mddev);
 			} else if (bio != NULL && bio->bi_status) {
 				fail = true;
-				narrow_write_error(r10_bio, m);
+				/* Mapping failures are whole-range and deterministic */
+				if (bio->bi_status == BLK_STS_P2PDMA)
+					rdev_set_badblocks(rdev,
+							   r10_bio->devs[m].addr,
+							   r10_bio->sectors, 0);
+				else
+					narrow_write_error(r10_bio, m);
 				rdev_dec_pending(rdev, conf->mddev);
 			}
 			bio = r10_bio->devs[m].repl_bio;
diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 6909e354279427..2f50509a7a6160 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1469,6 +1469,7 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,
 		int *count, int *pi_count)
 {
 	struct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);
+	struct sg_table sgt;
 	int ret;
 
 	req->data_sgl.sg_table.sgl = (struct scatterlist *)(req + 1);
@@ -1480,12 +1481,14 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,
 
 	req->data_sgl.nents = blk_rq_map_sg(rq, req->data_sgl.sg_table.sgl);
 
-	*count = ib_dma_map_sg(ibdev, req->data_sgl.sg_table.sgl,
-			       req->data_sgl.nents, rq_dma_dir(rq));
-	if (unlikely(*count <= 0)) {
-		ret = -EIO;
+	sgt = (struct sg_table) {
+		.sgl		= req->data_sgl.sg_table.sgl,
+		.orig_nents	= req->data_sgl.nents,
+	};
+	ret = ib_dma_map_sgtable_attrs(ibdev, &sgt, rq_dma_dir(rq), 0);
+	if (unlikely(ret))
 		goto out_free_table;
-	}
+	*count = sgt.nents;
 
 	if (blk_integrity_rq(rq)) {
 		req->metadata_sgl->sg_table.sgl =
@@ -1501,14 +1504,14 @@ static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,
 
 		req->metadata_sgl->nents = blk_rq_map_integrity_sg(rq,
 				req->metadata_sgl->sg_table.sgl);
-		*pi_count = ib_dma_map_sg(ibdev,
-					  req->metadata_sgl->sg_table.sgl,
-					  req->metadata_sgl->nents,
-					  rq_dma_dir(rq));
-		if (unlikely(*pi_count <= 0)) {
-			ret = -EIO;
+		sgt = (struct sg_table) {
+			.sgl		= req->metadata_sgl->sg_table.sgl,
+			.orig_nents	= req->metadata_sgl->nents,
+		};
+		ret = ib_dma_map_sgtable_attrs(ibdev, &sgt, rq_dma_dir(rq), 0);
+		if (unlikely(ret))
 			goto out_free_pi_table;
-		}
+		*pi_count = sgt.nents;
 	}
 
 	return 0;
@@ -2026,8 +2029,6 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
 	if (ret)
 		goto unmap_qe;
 
-	nvme_start_request(rq);
-
 	if (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) &&
 	    queue->pi_support &&
 	    (c->common.opcode == nvme_cmd_write ||
@@ -2039,11 +2040,13 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
 
 	err = nvme_rdma_map_data(queue, rq, c);
 	if (unlikely(err < 0)) {
-		dev_err(queue->ctrl->ctrl.device,
-			     "Failed to map data (%d)\n", err);
+		dev_err_ratelimited(queue->ctrl->ctrl.device,
+				    "Failed to map data (%d)\n", err);
 		goto err;
 	}
 
+	nvme_start_request(rq);
+
 	sqe->cqe.done = nvme_rdma_send_done;
 
 	ib_dma_sync_single_for_device(dev, sqe->dma,
@@ -2063,6 +2066,9 @@ static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
 		ret = nvme_host_path_error(rq);
 	else if (err == -ENOMEM || err == -EAGAIN)
 		ret = BLK_STS_RESOURCE;
+	/* Peer memory unreachable from this device: don't retry. */
+	else if (err == -EREMOTEIO)
+		ret = BLK_STS_P2PDMA;
 	else
 		ret = BLK_STS_IOERR;
 	nvme_cleanup_cmd(rq);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 8808ee76e73c09..c8de7809320ad4 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -165,6 +165,15 @@ typedef u16 blk_short_t;
  */
 #define BLK_STS_DURATION_LIMIT	((__force blk_status_t)17)
 
+/*
+ * BLK_STS_P2PDMA is returned when a peer-to-peer DMA transfer cannot be
+ * mapped (typically because there is no route between the initiator and the
+ * target that the platform's PCIe topology and ACS settings allow). This
+ * is a property of the initiator/target pair, not of the target device's
+ * health. This error should never be retried.
+ */
+#define BLK_STS_P2PDMA	((__force blk_status_t)18)
+
 /*
  * Invalid size or alignment.
  */
@@ -188,6 +197,7 @@ static inline bool blk_path_error(blk_status_t error)
 	case BLK_STS_NOTSUPP:
 	case BLK_STS_NOSPC:
 	case BLK_STS_TARGET:
+	case BLK_STS_P2PDMA:
 	case BLK_STS_RESV_CONFLICT:
 	case BLK_STS_MEDIUM:
 	case BLK_STS_PROTECTION:

3/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 7935
							output: 25
							thoughts: 499

Thoughts: 
**Analyzing the P2PDMA Patch**

Okay, so I've got this patch introducing `BLK_STS_P2PDMA`. It seems focused on handling Peer-to-Peer DMA errors, specifically when a P2PDMA transfer can't be mapped. The changes touch a pretty wide range of code: `blk-core.c`, `blk-mq-dma.c`, various RAID components (`md.c`, `raid1-10.c`, etc.), `nvme/host/rdma.c`, and `blk_types.h`. That's a decent spread. The core of it seems to be returning this new `BLK_STS_P2PDMA` status. The patch also modifies how MD (software RAID) handles P2PDMA bios, ensuring correct error handling without cascading failures and how NVMe RDMA handles mapping failures with `-EREMOTEIO`.

My primary concern, of course, is about reachability. Is this code path even *reachable* in a virtualized environment like GCE or QEMU? P2PDMA, by its very nature, relies on PCI devices with P2PDMA support. The real question is: can we emulate that in QEMU? We'd need to be able to trigger the P2PDMA logic, which leads me to my next question, is there any software emulated P2PDMA device that we could possibly use, or another way that this path can be triggered?

Specifically, I need to understand how the MD and NVMe changes come into play. In MD, the function `md_bio_is_p2pdma(bio)` is crucial. It calls `is_pci_p2pdma_page(bio->bi_io_vec->bv_page)`. Can we create a P2PDMA page *within* a virtualized environment? P2PDMA pages are typically created by PCI drivers using `pci_p2pdma_add_resource()`. My guess is that, without real hardware, this is going to be the tough part.

So, I'm thinking, is there *any* way to trigger this without physical hardware? Maybe a simulated environment, perhaps something in `drivers/nvme/target/p2pmem.c`, or something else entirely. I'm going to search the codebase for uses of `pci_p2pdma_add_resource` and `is_pci_p2pdma_page`. That should give me a better handle on the conditions needed to reach this code.

4/2 2026/07/23 21:33 tool grepper
0m Args: 
{
  "Expression": "pci_p2pdma_add_resource"
}

Results: 
{
  "Output": "Documentation/driver-api/pci/p2pdma.rst=95=A provider simply needs to register a BAR (or a portion of a BAR)\nDocumentation/driver-api/pci/p2pdma.rst:96:as a P2P DMA resource using :c:func:`pci_p2pdma_add_resource()`.\nDocumentation/driver-api/pci/p2pdma.rst-97-This will register struct pages for all the specified memory.\n--\ndrivers/accel/habanalabs/common/hldio.c=369=int hl_p2p_region_init(struct hl_device *hdev, struct hl_p2p_region *p2pr)\n--\ndrivers/accel/habanalabs/common/hldio.c-374-\t/* Start by publishing our p2p memory */\ndrivers/accel/habanalabs/common/hldio.c:375:\trc = pci_p2pdma_add_resource(hdev-\u003epdev, p2pr-\u003ebar, p2pr-\u003esize, p2pr-\u003ebar_offset);\ndrivers/accel/habanalabs/common/hldio.c-376-\tif (rc) {\n--\ndrivers/nvme/host/pci.c=2459=static void nvme_map_cmb(struct nvme_dev *dev)\n--\ndrivers/nvme/host/pci.c-2506-\ndrivers/nvme/host/pci.c:2507:\tif (pci_p2pdma_add_resource(pdev, bar, size, offset)) {\ndrivers/nvme/host/pci.c-2508-\t\tdev_warn(dev-\u003ectrl.device,\n--\ndrivers/pci/p2pdma.c=363=static void pci_p2pdma_unmap_mappings(void *data)\n--\ndrivers/pci/p2pdma.c-377-/**\ndrivers/pci/p2pdma.c:378: * pci_p2pdma_add_resource - add memory for use as p2p memory\ndrivers/pci/p2pdma.c-379- * @pdev: the device to add the memory to\n--\ndrivers/pci/p2pdma.c-386- */\ndrivers/pci/p2pdma.c:387:int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,\ndrivers/pci/p2pdma.c-388-\t\t\t    u64 offset)\n--\ndrivers/pci/p2pdma.c-466-}\ndrivers/pci/p2pdma.c:467:EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);\ndrivers/pci/p2pdma.c-468-\n--\ninclude/linux/pci-p2pdma.h=72=struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev, int bar);\ninclude/linux/pci-p2pdma.h:73:int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,\ninclude/linux/pci-p2pdma.h-74-\t\tu64 offset);\n--\ninclude/linux/pci-p2pdma.h=96=static inline struct p2pdma_provider *pcim_p2pdma_provider(struct pci_dev *pdev,\n--\ninclude/linux/pci-p2pdma.h-100-}\ninclude/linux/pci-p2pdma.h:101:static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,\ninclude/linux/pci-p2pdma.h-102-\t\tsize_t size, u64 offset)\n"
}
5/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 9996
							output: 25
							thoughts: 335

Thoughts: 
**Exploring P2PDMA and its Interaction with MD RAID**

Okay, so I'm digging into how P2PDMA works, specifically within the NVMe context and wondering about its integration with MD RAID. I see that `pci_p2pdma_add_resource` in `drivers/nvme/host/pci.c` is key, particularly for Controller Memory Buffer (CMB). My initial thought is, can this be emulated within a QEMU environment? Luckily, QEMU's NVMe device *does* support CMB, so that's promising – we can simulate P2PDMA pages in a virtualized setup.

Now, the interesting question is: can we actually trigger the MD RAID code using these P2PDMA pages? If we have an NVMe device configured with CMB, we should be able to treat it as a P2PDMA provider. The next logical step is, can we then use this P2PDMA setup to transfer data to *another* NVMe device or even an MD device?

I found that the patch modifies MD to handle these P2PDMA bios. Wait, `md_bio_is_p2pdma`! It checks if the bio has a P2PDMA page. So, if we create an MD array utilizing NVMe devices, and we issue a P2PDMA I/O *to* that MD array, it should pass the bio down to the underlying devices, right?

But, can this even be triggered from userspace? Usually, P2PDMA is the domain of kernel drivers. Think NVMe-oF target or RDMA. Oh, wait, `O_DIRECT` coupled with P2PDMA pages? No, that won't work. Userspace can't directly allocate P2PDMA pages. That closes that door.

Alright, so how *are* P2PDMA pages created and used? I need to dig deeper. I'll need to check the usage of `is_pci_p2pdma_page` or specifically how P2PDMA bios are created. That's the key to understanding this.

6/2 2026/07/23 21:33 tool grepper
0m Args: 
{
  "Expression": "is_pci_p2pdma_page"
}

Results: 
{
  "Output": "block/bio-integrity.c=333=static unsigned int bvec_from_pages(struct bio_vec *bvec, struct page **pages,\n--\nblock/bio-integrity.c-355-\nblock/bio-integrity.c:356:\t\tif (is_pci_p2pdma_page(pages[i]))\nblock/bio-integrity.c-357-\t\t\t*is_p2p = true;\n--\nblock/bio.c=1006=void __bio_add_page(struct bio *bio, struct page *page,\n--\nblock/bio.c-1011-\nblock/bio.c:1012:\tif (is_pci_p2pdma_page(page))\nblock/bio.c-1013-\t\tbio-\u003ebi_opf |= REQ_NOMERGE;\n--\nblock/bio.c=1245=int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter,\n--\nblock/bio.c-1277-\nblock/bio.c:1278:\tif (is_pci_p2pdma_page(bio-\u003ebi_io_vec-\u003ebv_page))\nblock/bio.c-1279-\t\tbio-\u003ebi_opf |= REQ_NOMERGE;\n--\nblock/blk.h=156=static inline bool zone_device_pages_compatible(const struct page *a,\n--\nblock/blk.h-158-{\nblock/blk.h:159:\tif (is_pci_p2pdma_page(a) || is_pci_p2pdma_page(b))\nblock/blk.h-160-\t\treturn zone_device_pages_have_same_pgmap(a, b);\n--\ndrivers/md/md.h=34=static inline bool md_bio_is_p2pdma(struct bio *bio)\n--\ndrivers/md/md.h-36-\treturn bio_has_data(bio) \u0026\u0026 bio-\u003ebi_io_vec \u0026\u0026\ndrivers/md/md.h:37:\t       is_pci_p2pdma_page(bio-\u003ebi_io_vec-\u003ebv_page);\ndrivers/md/md.h-38-}\n--\ndrivers/nvme/host/pci.c=1206=static blk_status_t nvme_pci_setup_data_simple(struct request *req,\n--\ndrivers/nvme/host/pci.c-1217-\t\treturn BLK_STS_AGAIN;\ndrivers/nvme/host/pci.c:1218:\tif (is_pci_p2pdma_page(bv.bv_page))\ndrivers/nvme/host/pci.c-1219-\t\treturn BLK_STS_AGAIN;\n--\ndrivers/nvme/host/pci.c=1372=static blk_status_t nvme_pci_setup_meta_mptr(struct request *req)\n--\ndrivers/nvme/host/pci.c-1377-\ndrivers/nvme/host/pci.c:1378:\tif (is_pci_p2pdma_page(bv.bv_page))\ndrivers/nvme/host/pci.c-1379-\t\treturn nvme_pci_setup_meta_iter(req);\n--\ndrivers/nvme/target/io-cmd-bdev.c=253=static void nvmet_bdev_execute_rw(struct nvmet_req *req)\n--\ndrivers/nvme/target/io-cmd-bdev.c-286-\ndrivers/nvme/target/io-cmd-bdev.c:287:\tif (is_pci_p2pdma_page(sg_page(req-\u003esg)))\ndrivers/nvme/target/io-cmd-bdev.c-288-\t\topf |= REQ_NOMERGE;\n--\ninclude/linux/memremap.h=192=static inline void folio_set_zone_device_data(struct folio *folio, void *data)\n--\ninclude/linux/memremap.h-197-\ninclude/linux/memremap.h:198:static inline bool is_pci_p2pdma_page(const struct page *page)\ninclude/linux/memremap.h-199-{\n--\ninclude/linux/pci-p2pdma.h=191=pci_p2pdma_state(struct pci_p2pdma_map_state *state, struct device *dev,\n--\ninclude/linux/pci-p2pdma.h-193-{\ninclude/linux/pci-p2pdma.h:194:\tif (IS_ENABLED(CONFIG_PCI_P2PDMA) \u0026\u0026 is_pci_p2pdma_page(page)) {\ninclude/linux/pci-p2pdma.h-195-\t\t__pci_p2pdma_update_state(state, dev, page);\n--\nmm/gup.c=517=static struct folio *try_grab_folio_fast(struct page *page, int refs,\n--\nmm/gup.c-527-\nmm/gup.c:528:\tif (unlikely(!(flags \u0026 FOLL_PCI_P2PDMA) \u0026\u0026 is_pci_p2pdma_page(page)))\nmm/gup.c-529-\t\treturn NULL;\n"
}
7/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 12177
							output: 25
							thoughts: 175

Thoughts: 
**Investigating P2PDMA Page Usage in Direct I/O**

Okay, so I see `is_pci_p2pdma_page` being called within `bio_iov_iter_get_pages`. That's interesting, because `bio_iov_iter_get_pages` is essential for direct I/O and NVMe target operations. A lightbulb went off: I recall `FOLL_PCI_P2PDMA` is a flag utilized by `get_user_pages`. This triggers the question – can userspace actually map P2PDMA pages and consequently perform direct I/O using them?

The answer seems to be yes, `O_DIRECT` *can* be used with these P2PDMA pages, provided they're appropriately mapped into userspace. Now, the next question is how this mapping actually occurs. Are we looking at something like `/dev/p2pmem*` devices, or a similar interface? Time to dig into `drivers/pci/p2pdma.c` and see if there's a character device or any similar mechanisms exposed that allow userland access.

8/2 2026/07/23 21:33 tool grepper
0m Error: 
no matches

Args: 
{
  "Expression": "pci_p2pdma_add_client"
}

Results: 
{
  "error": "no matches"
}
9/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 12633
							output: 34
							thoughts: 22

Thoughts: 
Here's my thought process, summarized as you requested:

**Investigating Userspace Mapping in PCI Direct Memory Access**

Alright, I need to refresh my memory on how userspace mapping is handled in the PCI Direct Memory Access (DMA) context within the kernel. The likely place to start looking is the `drivers/pci/p2pdma.c` file. That seems the most logical spot to find the core implementation and any related interactions with userspace. I'll focus my investigation there.

10/2 2026/07/23 21:33 tool grepper
0m Error: 
no matches

Args: 
{
  "Expression": "file_operations",
  "PathPrefix": "drivers/pci/p2pdma.c"
}

Results: 
{
  "error": "no matches"
}
11/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 12809
							output: 30
							thoughts: 50

Thoughts: 
**NVMe CMB and Userpace Mapping - A Quick Scan**

Okay, hold on a second. Did I just read something about NVMe CMB being accessible from userspace? That doesn't sound right... typically, you wouldn't expect that. Let me re-think that – no, usually it's not a direct mapping. But… could there be something I’m missing?

Alright, let's refocus. Perhaps the kernel's NVMe target code might hold a clue. Let me quickly zero in on `drivers/nvme/target/p2pmem.c`. I have a feeling that file might be relevant to understanding any potential nuances or workarounds related to this topic. Time to take a closer look!

12/2 2026/07/23 21:33 tool grepper
0m Args: 
{
  "Expression": "p2p",
  "PathPrefix": "drivers/nvme/target/"
}

Results: 
{
  "Output": "drivers/nvme/target/configfs.c-14-#include \u003clinux/pci.h\u003e\ndrivers/nvme/target/configfs.c:15:#include \u003clinux/pci-p2pdma.h\u003e\ndrivers/nvme/target/configfs.c-16-#ifdef CONFIG_NVME_TARGET_AUTH\n--\ndrivers/nvme/target/configfs.c=560=CONFIGFS_ATTR(nvmet_ns_, device_path);\n--\ndrivers/nvme/target/configfs.c-562-#ifdef CONFIG_PCI_P2PDMA\ndrivers/nvme/target/configfs.c:563:static ssize_t nvmet_ns_p2pmem_show(struct config_item *item, char *page)\ndrivers/nvme/target/configfs.c-564-{\n--\ndrivers/nvme/target/configfs.c-566-\ndrivers/nvme/target/configfs.c:567:\treturn pci_p2pdma_enable_show(page, ns-\u003ep2p_dev, ns-\u003euse_p2pmem);\ndrivers/nvme/target/configfs.c-568-}\ndrivers/nvme/target/configfs.c-569-\ndrivers/nvme/target/configfs.c:570:static ssize_t nvmet_ns_p2pmem_store(struct config_item *item,\ndrivers/nvme/target/configfs.c-571-\t\tconst char *page, size_t count)\n--\ndrivers/nvme/target/configfs.c-573-\tstruct nvmet_ns *ns = to_nvmet_ns(item);\ndrivers/nvme/target/configfs.c:574:\tstruct pci_dev *p2p_dev = NULL;\ndrivers/nvme/target/configfs.c:575:\tbool use_p2pmem;\ndrivers/nvme/target/configfs.c-576-\tint ret = count;\n--\ndrivers/nvme/target/configfs.c-584-\ndrivers/nvme/target/configfs.c:585:\terror = pci_p2pdma_enable_store(page, \u0026p2p_dev, \u0026use_p2pmem);\ndrivers/nvme/target/configfs.c-586-\tif (error) {\n--\ndrivers/nvme/target/configfs.c-590-\ndrivers/nvme/target/configfs.c:591:\tns-\u003euse_p2pmem = use_p2pmem;\ndrivers/nvme/target/configfs.c:592:\tpci_dev_put(ns-\u003ep2p_dev);\ndrivers/nvme/target/configfs.c:593:\tns-\u003ep2p_dev = p2p_dev;\ndrivers/nvme/target/configfs.c-594-\n--\ndrivers/nvme/target/configfs.c-600-\ndrivers/nvme/target/configfs.c:601:CONFIGFS_ATTR(nvmet_ns_, p2pmem);\ndrivers/nvme/target/configfs.c-602-#endif /* CONFIG_PCI_P2PDMA */\n--\ndrivers/nvme/target/configfs.c=825=static struct configfs_attribute *nvmet_ns_attrs[] = {\n--\ndrivers/nvme/target/configfs.c-834-#ifdef CONFIG_PCI_P2PDMA\ndrivers/nvme/target/configfs.c:835:\t\u0026nvmet_ns_attr_p2pmem,\ndrivers/nvme/target/configfs.c-836-#endif\n--\ndrivers/nvme/target/core.c-10-#include \u003clinux/rculist.h\u003e\ndrivers/nvme/target/core.c:11:#include \u003clinux/pci-p2pdma.h\u003e\ndrivers/nvme/target/core.c-12-#include \u003clinux/scatterlist.h\u003e\n--\ndrivers/nvme/target/core.c=477=static void nvmet_ns_dev_disable(struct nvmet_ns *ns)\n--\ndrivers/nvme/target/core.c-482-\ndrivers/nvme/target/core.c:483:static int nvmet_p2pmem_ns_enable(struct nvmet_ns *ns)\ndrivers/nvme/target/core.c-484-{\ndrivers/nvme/target/core.c-485-\tint ret;\ndrivers/nvme/target/core.c:486:\tstruct pci_dev *p2p_dev;\ndrivers/nvme/target/core.c-487-\ndrivers/nvme/target/core.c:488:\tif (!ns-\u003euse_p2pmem)\ndrivers/nvme/target/core.c-489-\t\treturn 0;\n--\ndrivers/nvme/target/core.c-495-\ndrivers/nvme/target/core.c:496:\tif (!blk_queue_pci_p2pdma(ns-\u003ebdev-\u003ebd_disk-\u003equeue)) {\ndrivers/nvme/target/core.c-497-\t\tpr_err(\"peer-to-peer DMA is not supported by the driver of %s\\n\",\n--\ndrivers/nvme/target/core.c-501-\ndrivers/nvme/target/core.c:502:\tif (ns-\u003ep2p_dev) {\ndrivers/nvme/target/core.c:503:\t\tret = pci_p2pdma_distance(ns-\u003ep2p_dev, nvmet_ns_dev(ns), true);\ndrivers/nvme/target/core.c-504-\t\tif (ret \u003c 0)\n--\ndrivers/nvme/target/core.c-507-\t\t/*\ndrivers/nvme/target/core.c:508:\t\t * Right now we just check that there is p2pmem available so\ndrivers/nvme/target/core.c-509-\t\t * we can report an error to the user right away if there\n--\ndrivers/nvme/target/core.c-513-\ndrivers/nvme/target/core.c:514:\t\tp2p_dev = pci_p2pmem_find(nvmet_ns_dev(ns));\ndrivers/nvme/target/core.c:515:\t\tif (!p2p_dev) {\ndrivers/nvme/target/core.c-516-\t\t\tpr_err(\"no peer-to-peer memory is available for %s\\n\",\n--\ndrivers/nvme/target/core.c-520-\ndrivers/nvme/target/core.c:521:\t\tpci_dev_put(p2p_dev);\ndrivers/nvme/target/core.c-522-\t}\n--\ndrivers/nvme/target/core.c-526-\ndrivers/nvme/target/core.c:527:static void nvmet_p2pmem_ns_add_p2p(struct nvmet_ctrl *ctrl,\ndrivers/nvme/target/core.c-528-\t\t\t\t    struct nvmet_ns *ns)\n--\ndrivers/nvme/target/core.c-530-\tstruct device *clients[2];\ndrivers/nvme/target/core.c:531:\tstruct pci_dev *p2p_dev;\ndrivers/nvme/target/core.c-532-\tint ret;\n--\ndrivers/nvme/target/core.c-535-\ndrivers/nvme/target/core.c:536:\tif (!ctrl-\u003ep2p_client || !ns-\u003euse_p2pmem)\ndrivers/nvme/target/core.c-537-\t\treturn;\ndrivers/nvme/target/core.c-538-\ndrivers/nvme/target/core.c:539:\tif (ns-\u003ep2p_dev) {\ndrivers/nvme/target/core.c:540:\t\tret = pci_p2pdma_distance(ns-\u003ep2p_dev, ctrl-\u003ep2p_client, true);\ndrivers/nvme/target/core.c-541-\t\tif (ret \u003c 0)\n--\ndrivers/nvme/target/core.c-543-\ndrivers/nvme/target/core.c:544:\t\tp2p_dev = pci_dev_get(ns-\u003ep2p_dev);\ndrivers/nvme/target/core.c-545-\t} else {\ndrivers/nvme/target/core.c:546:\t\tclients[0] = ctrl-\u003ep2p_client;\ndrivers/nvme/target/core.c-547-\t\tclients[1] = nvmet_ns_dev(ns);\ndrivers/nvme/target/core.c-548-\ndrivers/nvme/target/core.c:549:\t\tp2p_dev = pci_p2pmem_find_many(clients, ARRAY_SIZE(clients));\ndrivers/nvme/target/core.c:550:\t\tif (!p2p_dev) {\ndrivers/nvme/target/core.c-551-\t\t\tpr_err(\"no peer-to-peer memory is available that's supported by %s and %s\\n\",\ndrivers/nvme/target/core.c:552:\t\t\t       dev_name(ctrl-\u003ep2p_client), ns-\u003edevice_path);\ndrivers/nvme/target/core.c-553-\t\t\treturn;\n--\ndrivers/nvme/target/core.c-556-\ndrivers/nvme/target/core.c:557:\tret = radix_tree_insert(\u0026ctrl-\u003ep2p_ns_map, ns-\u003ensid, p2p_dev);\ndrivers/nvme/target/core.c-558-\tif (ret \u003c 0)\ndrivers/nvme/target/core.c:559:\t\tpci_dev_put(p2p_dev);\ndrivers/nvme/target/core.c-560-\ndrivers/nvme/target/core.c:561:\tpr_info(\"using p2pmem on %s for nsid %d\\n\", pci_name(p2p_dev),\ndrivers/nvme/target/core.c-562-\t\tns-\u003ensid);\n--\ndrivers/nvme/target/core.c=577=int nvmet_ns_enable(struct nvmet_ns *ns)\n--\ndrivers/nvme/target/core.c-599-\ndrivers/nvme/target/core.c:600:\tret = nvmet_p2pmem_ns_enable(ns);\ndrivers/nvme/target/core.c-601-\tif (ret)\n--\ndrivers/nvme/target/core.c-604-\tlist_for_each_entry(ctrl, \u0026subsys-\u003ectrls, subsys_entry)\ndrivers/nvme/target/core.c:605:\t\tnvmet_p2pmem_ns_add_p2p(ctrl, ns);\ndrivers/nvme/target/core.c-606-\n--\ndrivers/nvme/target/core.c-627-\tlist_for_each_entry(ctrl, \u0026subsys-\u003ectrls, subsys_entry)\ndrivers/nvme/target/core.c:628:\t\tpci_dev_put(radix_tree_delete(\u0026ctrl-\u003ep2p_ns_map, ns-\u003ensid));\ndrivers/nvme/target/core.c-629-out_dev_disable:\n--\ndrivers/nvme/target/core.c=634=void nvmet_ns_disable(struct nvmet_ns *ns)\n--\ndrivers/nvme/target/core.c-646-\tlist_for_each_entry(ctrl, \u0026subsys-\u003ectrls, subsys_entry)\ndrivers/nvme/target/core.c:647:\t\tpci_dev_put(radix_tree_delete(\u0026ctrl-\u003ep2p_ns_map, ns-\u003ensid));\ndrivers/nvme/target/core.c-648-\n--\ndrivers/nvme/target/core.c=1288=static unsigned int nvmet_data_transfer_len(struct nvmet_req *req)\n--\ndrivers/nvme/target/core.c-1292-\ndrivers/nvme/target/core.c:1293:static int nvmet_req_alloc_p2pmem_sgls(struct pci_dev *p2p_dev,\ndrivers/nvme/target/core.c-1294-\t\tstruct nvmet_req *req)\ndrivers/nvme/target/core.c-1295-{\ndrivers/nvme/target/core.c:1296:\treq-\u003esg = pci_p2pmem_alloc_sgl(p2p_dev, \u0026req-\u003esg_cnt,\ndrivers/nvme/target/core.c-1297-\t\t\tnvmet_data_transfer_len(req));\n--\ndrivers/nvme/target/core.c-1301-\tif (req-\u003emetadata_len) {\ndrivers/nvme/target/core.c:1302:\t\treq-\u003emetadata_sg = pci_p2pmem_alloc_sgl(p2p_dev,\ndrivers/nvme/target/core.c-1303-\t\t\t\t\u0026req-\u003emetadata_sg_cnt, req-\u003emetadata_len);\n--\ndrivers/nvme/target/core.c-1307-\ndrivers/nvme/target/core.c:1308:\treq-\u003ep2p_dev = p2p_dev;\ndrivers/nvme/target/core.c-1309-\n--\ndrivers/nvme/target/core.c-1311-out_free_sg:\ndrivers/nvme/target/core.c:1312:\tpci_p2pmem_free_sgl(req-\u003ep2p_dev, req-\u003esg);\ndrivers/nvme/target/core.c-1313-out_err:\n--\ndrivers/nvme/target/core.c-1316-\ndrivers/nvme/target/core.c:1317:static struct pci_dev *nvmet_req_find_p2p_dev(struct nvmet_req *req)\ndrivers/nvme/target/core.c-1318-{\n--\ndrivers/nvme/target/core.c-1321-\t\treturn NULL;\ndrivers/nvme/target/core.c:1322:\treturn radix_tree_lookup(\u0026req-\u003esq-\u003ectrl-\u003ep2p_ns_map, req-\u003ens-\u003ensid);\ndrivers/nvme/target/core.c-1323-}\n--\ndrivers/nvme/target/core.c=1325=int nvmet_req_alloc_sgls(struct nvmet_req *req)\ndrivers/nvme/target/core.c-1326-{\ndrivers/nvme/target/core.c:1327:\tstruct pci_dev *p2p_dev = nvmet_req_find_p2p_dev(req);\ndrivers/nvme/target/core.c-1328-\ndrivers/nvme/target/core.c:1329:\tif (p2p_dev \u0026\u0026 !nvmet_req_alloc_p2pmem_sgls(p2p_dev, req))\ndrivers/nvme/target/core.c-1330-\t\treturn 0;\n--\ndrivers/nvme/target/core.c=1352=void nvmet_req_free_sgls(struct nvmet_req *req)\ndrivers/nvme/target/core.c-1353-{\ndrivers/nvme/target/core.c:1354:\tif (req-\u003ep2p_dev) {\ndrivers/nvme/target/core.c:1355:\t\tpci_p2pmem_free_sgl(req-\u003ep2p_dev, req-\u003esg);\ndrivers/nvme/target/core.c-1356-\t\tif (req-\u003emetadata_sg)\ndrivers/nvme/target/core.c:1357:\t\t\tpci_p2pmem_free_sgl(req-\u003ep2p_dev, req-\u003emetadata_sg);\ndrivers/nvme/target/core.c:1358:\t\treq-\u003ep2p_dev = NULL;\ndrivers/nvme/target/core.c-1359-\t} else {\n--\ndrivers/nvme/target/core.c=1532=bool nvmet_host_allowed(struct nvmet_subsys *subsys, const char *hostnqn)\n--\ndrivers/nvme/target/core.c-1551-\ndrivers/nvme/target/core.c:1552:static void nvmet_setup_p2p_ns_map(struct nvmet_ctrl *ctrl,\ndrivers/nvme/target/core.c:1553:\t\tstruct device *p2p_client)\ndrivers/nvme/target/core.c-1554-{\n--\ndrivers/nvme/target/core.c-1559-\ndrivers/nvme/target/core.c:1560:\tif (!p2p_client)\ndrivers/nvme/target/core.c-1561-\t\treturn;\ndrivers/nvme/target/core.c-1562-\ndrivers/nvme/target/core.c:1563:\tctrl-\u003ep2p_client = get_device(p2p_client);\ndrivers/nvme/target/core.c-1564-\ndrivers/nvme/target/core.c-1565-\tnvmet_for_each_enabled_ns(\u0026ctrl-\u003esubsys-\u003enamespaces, idx, ns)\ndrivers/nvme/target/core.c:1566:\t\tnvmet_p2pmem_ns_add_p2p(ctrl, ns);\ndrivers/nvme/target/core.c-1567-}\ndrivers/nvme/target/core.c-1568-\ndrivers/nvme/target/core.c:1569:static void nvmet_release_p2p_ns_map(struct nvmet_ctrl *ctrl)\ndrivers/nvme/target/core.c-1570-{\n--\ndrivers/nvme/target/core.c-1575-\ndrivers/nvme/target/core.c:1576:\tradix_tree_for_each_slot(slot, \u0026ctrl-\u003ep2p_ns_map, \u0026iter, 0)\ndrivers/nvme/target/core.c-1577-\t\tpci_dev_put(radix_tree_deref_slot(slot));\ndrivers/nvme/target/core.c-1578-\ndrivers/nvme/target/core.c:1579:\tput_device(ctrl-\u003ep2p_client);\ndrivers/nvme/target/core.c-1580-}\n--\ndrivers/nvme/target/core.c=1591=struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_alloc_ctrl_args *args)\n--\ndrivers/nvme/target/core.c-1637-\tINIT_LIST_HEAD(\u0026ctrl-\u003easync_events);\ndrivers/nvme/target/core.c:1638:\tINIT_RADIX_TREE(\u0026ctrl-\u003ep2p_ns_map, GFP_KERNEL);\ndrivers/nvme/target/core.c-1639-\tINIT_WORK(\u0026ctrl-\u003efatal_err_work, nvmet_fatal_error_handler);\n--\ndrivers/nvme/target/core.c-1691-\tlist_add_tail(\u0026ctrl-\u003esubsys_entry, \u0026subsys-\u003ectrls);\ndrivers/nvme/target/core.c:1692:\tnvmet_setup_p2p_ns_map(ctrl, args-\u003ep2p_client);\ndrivers/nvme/target/core.c-1693-\tnvmet_debugfs_ctrl_setup(ctrl);\n--\ndrivers/nvme/target/core.c=1741=static void nvmet_ctrl_free(struct kref *ref)\n--\ndrivers/nvme/target/core.c-1747-\tnvmet_ctrl_destroy_pr(ctrl);\ndrivers/nvme/target/core.c:1748:\tnvmet_release_p2p_ns_map(ctrl);\ndrivers/nvme/target/core.c-1749-\tlist_del(\u0026ctrl-\u003esubsys_entry);\n--\ndrivers/nvme/target/fabrics-cmd.c=267=static void nvmet_execute_admin_connect(struct nvmet_req *req)\n--\ndrivers/nvme/target/fabrics-cmd.c-275-\t\t.ops = req-\u003eops,\ndrivers/nvme/target/fabrics-cmd.c:276:\t\t.p2p_client = req-\u003ep2p_client,\ndrivers/nvme/target/fabrics-cmd.c-277-\t\t.kato = le32_to_cpu(c-\u003ekato),\n--\ndrivers/nvme/target/io-cmd-bdev.c=253=static void nvmet_bdev_execute_rw(struct nvmet_req *req)\n--\ndrivers/nvme/target/io-cmd-bdev.c-286-\ndrivers/nvme/target/io-cmd-bdev.c:287:\tif (is_pci_p2pdma_page(sg_page(req-\u003esg)))\ndrivers/nvme/target/io-cmd-bdev.c-288-\t\topf |= REQ_NOMERGE;\n--\ndrivers/nvme/target/nvmet.h=100=struct nvmet_ns {\n--\ndrivers/nvme/target/nvmet.h-123-\ndrivers/nvme/target/nvmet.h:124:\tstruct pci_dev\t\t*p2p_dev;\ndrivers/nvme/target/nvmet.h:125:\tint\t\t\tuse_p2pmem;\ndrivers/nvme/target/nvmet.h-126-\tint\t\t\tpi_type;\n--\ndrivers/nvme/target/nvmet.h=252=struct nvmet_ctrl {\n--\ndrivers/nvme/target/nvmet.h-290-\ndrivers/nvme/target/nvmet.h:291:\tstruct device\t\t*p2p_client;\ndrivers/nvme/target/nvmet.h:292:\tstruct radix_tree_root\tp2p_ns_map;\ndrivers/nvme/target/nvmet.h-293-#ifdef CONFIG_NVME_TARGET_DEBUGFS\n--\ndrivers/nvme/target/nvmet.h=447=struct nvmet_req {\n--\ndrivers/nvme/target/nvmet.h-492-\ndrivers/nvme/target/nvmet.h:493:\tstruct pci_dev\t\t*p2p_dev;\ndrivers/nvme/target/nvmet.h:494:\tstruct device\t\t*p2p_client;\ndrivers/nvme/target/nvmet.h-495-\tu16\t\t\terror_loc;\n--\ndrivers/nvme/target/nvmet.h=605=struct nvmet_alloc_ctrl_args {\n--\ndrivers/nvme/target/nvmet.h-611-\tconst struct nvmet_fabrics_ops *ops;\ndrivers/nvme/target/nvmet.h:612:\tstruct device\t\t*p2p_client;\ndrivers/nvme/target/nvmet.h-613-\tu32\t\t\tkato;\n--\ndrivers/nvme/target/rdma.c=400=static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,\n--\ndrivers/nvme/target/rdma.c-412-\ndrivers/nvme/target/rdma.c:413:\tif (ib_dma_pci_p2p_dma_supported(ndev-\u003edevice))\ndrivers/nvme/target/rdma.c:414:\t\tr-\u003ereq.p2p_client = \u0026ndev-\u003edevice-\u003edev;\ndrivers/nvme/target/rdma.c-415-\tr-\u003esend_sge.length = sizeof(*r-\u003ereq.cqe);\n"
}
13/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 19136
							output: 42
							thoughts: 566

Thoughts: 
**Reaching the Target: A Fuzzing Strategy**

Okay, so I've been digging into this, and it looks like `drivers/nvme/target/core.c` has P2P support built in.  That's key.  It uses `pci_p2pmem_alloc_sgl`, which is precisely what we want, and importantly, it's controllable via configfs using the `p2pmem` option. Bingo.

My immediate thought is, if we set up an NVMe target using an MD array as a backend – a `nvmet_ns` backed by a block device which itself is an MD array – and then enable `p2pmem` on that namespace... boom. The NVMe target *should* start allocating P2P memory and then issuing I/O directly to the MD array, using those pages. That triggers the MD RAID code we are interested in. This is definitely a solid attack surface.

And here's the kicker: this is all achievable in a virtualized environment with QEMU.  We can provision a virtual NVMe device with a CMB (Controller Memory Buffer) acting as a P2P memory provider. And yes, QEMU's NVMe device *does* support CMB, thanks to the `cmb_size_mb` parameter.

Now, does syzkaller play nicely?  Yes! It has descriptions for NVMe target configfs, so that's covered. Also, it has descriptions for MD ioctls, so we can define the MD arrays.  This is all definitely reachable and ripe for fuzzing.

Moving on, I need to check out the NVMe RDMA modifications in `drivers/nvme/host/rdma.c`. It looks like the patch changes `nvme_rdma_dma_map_req` to use `ib_dma_map_sgtable_attrs` instead of the old `ib_dma_map_sg`.  We're mapping the scatterlist.

Also, in `nvme_rdma_queue_rq`, it handles `-EREMOTEIO` by returning `BLK_STS_P2PDMA`. This is also a valid pathway if we're using NVMe over RDMA, which syzkaller supports with its `siw` or `rxe` software RDMA drivers.

Now I'm thinking, does software RDMA support P2PDMA?  `ib_dma_pci_p2p_dma_supported` is checked in `nvmet_rdma_alloc_rsp`, but the code in `nvme_rdma_dma_map_req` seems to execute for *all* NVMe RDMA requests, not just P2PDMA ones!  I need to confirm that last point... I'll verify this.

14/2 2026/07/23 21:33 tool grepper
0m Args: 
{
  "Expression": "ib_dma_map_sgtable_attrs",
  "PathPrefix": "drivers/nvme/host/rdma.c"
}

Results: 
{
  "Output": "drivers/nvme/host/rdma.c=1468=static int nvme_rdma_dma_map_req(struct ib_device *ibdev, struct request *rq,\n--\ndrivers/nvme/host/rdma.c-1487-\t};\ndrivers/nvme/host/rdma.c:1488:\tret = ib_dma_map_sgtable_attrs(ibdev, \u0026sgt, rq_dma_dir(rq), 0);\ndrivers/nvme/host/rdma.c-1489-\tif (unlikely(ret))\n--\ndrivers/nvme/host/rdma.c-1510-\t\t};\ndrivers/nvme/host/rdma.c:1511:\t\tret = ib_dma_map_sgtable_attrs(ibdev, \u0026sgt, rq_dma_dir(rq), 0);\ndrivers/nvme/host/rdma.c-1512-\t\tif (unlikely(ret))\n"
}
15/2 2026/07/23 21:33 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 20608
							output: 26
							thoughts: 431

Thoughts: 
**Analyzing the NVMe RDMA and MD RAID Modifications**

Okay, so looking at this patch, the core change for NVMe RDMA, specifically the switch in `nvme_rdma_dma_map_req` to `ib_dma_map_sgtable_attrs`, seems like a solid functional change affecting all NVMe RDMA I/O. The NVMe RDMA component is definitely reachable and testable, which is good. We don't necessarily need P2PDMA to validate the fundamental RDMA part.

Now, the more interesting part is the modifications to the MD RAID code. It's touching a number of functions, primarily around how P2PDMA bios are handled: `md_submit_bio` now sets `REQ_NOMERGE`, `raid1_write_error` is modified to avoid disk failures under specific P2PDMA conditions, and changes extend to `raid1_end_write_request`, `raid1_write_request`, `handle_write_finished`, and `handle_read_error` to handle P2PDMA errors, like blocking the bio if we get a `p2pdma_error`. There are similar changes for RAID10, too.

To test these MD RAID modifications thoroughly, though, we absolutely need to generate P2PDMA bios. Can Syzkaller do that? Ah, yes! If Syzkaller configures an NVMe target with `p2pmem` and points it to an MD array, then all I/O to that NVMe target should generate the appropriate P2PDMA bios to the MD array, which is a nice specific way to validate these. This is a very specific setup, but functionally reachable, which is key.

Even if syzkaller doesn't make it *easy* to generate P2PDMA bios directly, I should remember that the MD RAID changes aren't *exclusively* P2PDMA-focused. Some of the changes, like the refactoring of `raid1_write_error` as a helper function, and the `CollisionCheck` change impact *normal* bios, too. Wait, what was that `CollisionCheck` change all about? I should probably give that another look.

16/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "CollisionCheck",
  "PathPrefix": "drivers/md/"
}

Results: 
{
  "Output": "drivers/md/md.c=154=static void rdev_uninit_serial(struct md_rdev *rdev)\ndrivers/md/md.c-155-{\ndrivers/md/md.c:156:\tif (!test_and_clear_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/md.c-157-\t\treturn;\n--\ndrivers/md/md.c=171=static int rdev_init_serial(struct md_rdev *rdev)\n--\ndrivers/md/md.c-176-\ndrivers/md/md.c:177:\tif (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/md.c-178-\t\treturn 0;\n--\ndrivers/md/md.c-192-\trdev-\u003eserial = serial;\ndrivers/md/md.c:193:\tset_bit(CollisionCheck, \u0026rdev-\u003eflags);\ndrivers/md/md.c-194-\n--\ndrivers/md/md.c=233=void mddev_create_serial_pool(struct mddev *mddev, struct md_rdev *rdev)\n--\ndrivers/md/md.c-237-\tif (rdev \u0026\u0026 !rdev_need_serial(rdev) \u0026\u0026\ndrivers/md/md.c:238:\t    !test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/md.c-239-\t\treturn;\n--\ndrivers/md/md.c-264- * Free resource from rdev(s), and destroy serial_info_pool under conditions:\ndrivers/md/md.c:265: * 1. rdev is the last device flaged with CollisionCheck.\ndrivers/md/md.c-266- * 2. when bitmap is destroyed while policy is not enabled.\n--\ndrivers/md/md.c=269=void mddev_destroy_serial_pool(struct mddev *mddev, struct md_rdev *rdev)\ndrivers/md/md.c-270-{\ndrivers/md/md.c:271:\tif (rdev \u0026\u0026 !test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/md.c-272-\t\treturn;\n--\ndrivers/md/md.c-286-\t\t\t} else if (temp != rdev \u0026\u0026\ndrivers/md/md.c:287:\t\t\t\t   test_bit(CollisionCheck, \u0026temp-\u003eflags))\ndrivers/md/md.c-288-\t\t\t\tnum++;\n--\ndrivers/md/md.h=242=enum flag_bits {\n--\ndrivers/md/md.h-306-\t\t\t\t */\ndrivers/md/md.h:307:\tCollisionCheck,\t\t/*\ndrivers/md/md.h-308-\t\t\t\t * check if there is collision between raid1\n--\ndrivers/md/raid1.c=469=static void raid1_end_write_request(struct bio *bio)\n--\ndrivers/md/raid1.c-533-\tif (behind) {\ndrivers/md/raid1.c:534:\t\tif (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/raid1.c-535-\t\t\tremove_serial(rdev, lo, hi);\n--\ndrivers/md/raid1.c-557-\t\t}\ndrivers/md/raid1.c:558:\t} else if (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/raid1.c-559-\t\tremove_serial(rdev, lo, hi);\n--\ndrivers/md/raid1.c=1506=static bool raid1_write_request(struct mddev *mddev, struct bio *bio,\n--\ndrivers/md/raid1.c-1666-\t\t\t\t\t       GFP_NOIO, \u0026mddev-\u003ebio_set);\ndrivers/md/raid1.c:1667:\t\t\tif (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/raid1.c-1668-\t\t\t\twait_for_serialization(rdev, r1_bio);\n--\ndrivers/md/raid1.c-1675-\t\t\t/*\ndrivers/md/raid1.c:1676:\t\t\t * CollisionCheck marks every rdev with a serial\ndrivers/md/raid1.c-1677-\t\t\t * tree; order against in-flight write-behind I/O.\ndrivers/md/raid1.c-1678-\t\t\t */\ndrivers/md/raid1.c:1679:\t\t\tif (test_bit(CollisionCheck, \u0026rdev-\u003eflags))\ndrivers/md/raid1.c-1680-\t\t\t\twait_for_serialization(rdev, r1_bio);\n"
}
17/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 22730
							output: 53
							thoughts: 908

Thoughts: 
**Fuzzing Target Refinement: Block Layer, MD RAID, and NVMe RDMA Integration**

Okay, so looking at this patch, it seems like a bunch of interconnected changes. First, it looks like `CollisionCheck` is now the serialization flag being used in `raid1_end_write_request` and `raid1_write_request`, replacing the previous `MD_SERIALIZE_POLICY` on `mddev`. This is a functional change affecting the RAID1 write path, even independent of P2PDMA.

Let me break down what this patch is doing more broadly:

1.  **Block Layer Updates:** The patch introduces `BLK_STS_P2PDMA` status code. `blk-mq-dma.c` is updated to return this new code in the appropriate situations, specifically related to PCI P2PDMA mapping issues.
2.  **MD RAID Integration:** Several MD RAID files (`md.c`, `raid1.c`, `raid10.c`) see changes. There's a new `md_bio_is_p2pdma` check and `REQ_NOMERGE` is set for P2PDMA bios. More importantly, error handling is altered to handle the new `BLK_STS_P2PDMA` status, handling badblocks. And the serialization check has changed as mentioned above.
3.  **NVMe RDMA DMA Mapping:** `rdma.c` uses a different DMA mapping API (`ib_dma_map_sgtable_attrs` instead of `ib_dma_map_sg`) and returns `BLK_STS_P2PDMA` in the case of `-EREMOTEIO`.

Given these changes, this is *definitely* worth fuzzing. The patch modifies core block layer error codes, MD RAID error handling and serialization logic, and NVMe RDMA DMA mapping, so it touches critical paths.

Now, let's refine the list of specific symbols to focus on:

I think `raid1_write_error`, `handle_write_finished`, `handle_read_error` and `narrow_write_error` (in raid1 and raid10) are good, since they deal with the error paths. `nvme_rdma_dma_map_req` and `nvme_rdma_queue_rq` are also important because the DMA mapping API was modified. `raid1_write_request` is a hot path but specific to RAID1 and I will drop it for the moment.

So, here's my narrowed-down list:

*   `raid1_write_error` (static)
*   `handle_write_finished` (raid1 and raid10)
*   `handle_read_error` (raid1 and raid10)
*   `narrow_write_error` (raid1 and raid10)
*   `nvme_rdma_dma_map_req` (static)
*   `nvme_rdma_queue_rq`

I'll double-check those names within the RAID1 and RAID10 driver files to be extra sure, but I feel good about this list to start.

18/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "^(static )?(void|int|bool) (handle_write_finished|handle_read_error|narrow_write_error)",
  "PathPrefix": "drivers/md/"
}

Results: 
{
  "Output": "drivers/md/raid1.c=2431=static void fix_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n--\ndrivers/md/raid1.c-2515-\ndrivers/md/raid1.c:2516:static void narrow_write_error(struct r1bio *r1_bio, int i)\ndrivers/md/raid1.c-2517-{\n--\ndrivers/md/raid1.c=2590=static void handle_sync_write_finished(struct r1conf *conf, struct r1bio *r1_bio)\n--\ndrivers/md/raid1.c-2609-\ndrivers/md/raid1.c:2610:static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)\ndrivers/md/raid1.c-2611-{\n--\ndrivers/md/raid1.c-2656-\ndrivers/md/raid1.c:2657:static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)\ndrivers/md/raid1.c-2658-{\n--\ndrivers/md/raid10.c=2626=static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10bio *r10_bio)\n--\ndrivers/md/raid10.c-2780-\ndrivers/md/raid10.c:2781:static void narrow_write_error(struct r10bio *r10_bio, int i)\ndrivers/md/raid10.c-2782-{\n--\ndrivers/md/raid10.c-2846-\ndrivers/md/raid10.c:2847:static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)\ndrivers/md/raid10.c-2848-{\n"
}
19/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 24888
							output: 33
							thoughts: 43

Thoughts: 
Okay, let's see... I'm looking at this code and something's immediately off. Hang on a second, why are they using `handle_write_completed` in `raid10.c`? My mental model definitely has me expecting `handle_write_finished` in that context. That feels like a subtle but potentially critical mismatch, especially with RAID10's complexities. Right, time to dig into the patch history for `raid10.c`. I need to understand why this choice was made. It's possible there's a good reason that’s not immediately apparent, or worse, it’s a bug. Either way, understanding the rationale behind this is crucial before I can sign off on this. Let's see what the change log has to say...

20/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "handle_write_",
  "PathPrefix": "drivers/md/raid10.c"
}

Results: 
{
  "Output": "drivers/md/raid10.c=2847=static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)\n--\ndrivers/md/raid10.c-2887-\ndrivers/md/raid10.c:2888:static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)\ndrivers/md/raid10.c-2889-{\n--\ndrivers/md/raid10.c=2985=static void raid10d(struct md_thread *thread)\n--\ndrivers/md/raid10.c-3037-\t\t    test_bit(R10BIO_WriteError, \u0026r10_bio-\u003estate))\ndrivers/md/raid10.c:3038:\t\t\thandle_write_completed(conf, r10_bio);\ndrivers/md/raid10.c-3039-\t\telse if (test_bit(R10BIO_IsReshape, \u0026r10_bio-\u003estate))\n"
}
21/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 25410
							output: 21
							thoughts: 235

Thoughts: 
**My Current Assessment of the RAID10 Write Completion Handling**

Okay, so I'm zeroing in on `handle_write_completed` within `raid10.c`. This is where the core logic resides, and I need to understand it completely. My main focus is on the relevant error handling and completion pathways.

I've identified the key symbols that I need to keep in mind throughout the analysis: `raid1_write_error`, `narrow_write_error`, `handle_write_finished`, naturally `handle_write_completed` itself, `handle_read_error`, and also the RDMA related functions `nvme_rdma_dma_map_req` and `nvme_rdma_queue_rq`. Understanding how these interact will provide a picture of the error handling and P2PDMA integration.

Next, I need to make sure I understand the necessary build configurations. Based on my current knowledge, I'm expecting to see these activated: `CONFIG_MD_RAID1`, `CONFIG_MD_RAID10`, `CONFIG_NVME_RDMA`, and crucially, `CONFIG_PCI_P2PDMA` because that's what's driving this P2PDMA support. I should also see `CONFIG_NVME_TARGET` and `CONFIG_NVME_TARGET_CONFIGFS` which allow the NVMe target to be set up and configured with p2pmem. I should really confirm that `CONFIG_PCI_P2PDMA` is actually the correct name for the feature.

22/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "config PCI_P2PDMA"
}

Results: 
{
  "Output": "drivers/pci/Kconfig=197=config PCIE_TPH\n--\ndrivers/pci/Kconfig-205-\ndrivers/pci/Kconfig:206:config PCI_P2PDMA\ndrivers/pci/Kconfig-207-\tbool \"PCI peer-to-peer transfer support\"\n"
}
23/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 26088
							output: 20
							thoughts: 24

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

**Checking the PCIe Interconnect and NVMe RDMA Configuration**

Right, `PCI_P2PDMA`. Affirmative, that's what we're dealing with. Need to keep that in mind as we proceed. Now, given the direction we are headed, let's verify that the `CONFIG_NVME_RDMA` configuration option is set correctly. We should confirm that Remote Direct Memory Access is enabled for NVMe. That setting will be critical for our overall performance profile, especially given the context of P2PDMA. Best to double-check now and avoid any potential hiccups further down the line. It's easy enough to confirm, and vital to confirm our architecture is configured correctly.

24/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "config NVME_RDMA"
}

Results: 
{
  "Output": "drivers/nvme/host/Kconfig=47=config NVME_FABRICS\n--\ndrivers/nvme/host/Kconfig-51-\ndrivers/nvme/host/Kconfig:52:config NVME_RDMA\ndrivers/nvme/host/Kconfig-53-\ttristate \"NVM Express over Fabrics RDMA host driver\"\n"
}
25/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 26397
							output: 20
							thoughts: 34

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

**Kernel Configuration Verification**

Alright, yep, looks like we're looking at `NVME_RDMA`. Good, that's what I expected to see.

Now, let's just quickly confirm a few related configurations. I want to double-check that `CONFIG_MD_RAID1` and `CONFIG_MD_RAID10` are properly set. It's always a good practice to ensure those are enabled, especially when working with modern storage stacks and potential RDMA integration. These RAID levels, while seemingly straightforward, can interact in nuanced ways with NVMe and RDMA, so a quick verification is warranted. No surprises, just a sanity check before we dig deeper.

26/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "config MD_RAID1"
}

Results: 
{
  "Output": "drivers/md/Kconfig=104=config MD_RAID0\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"
}
27/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 26773
							output: 19
							thoughts: 31

Thoughts: 
Okay, here's my summary, presented as a stream of thought:

**Checking Storage Configuration**

Right, so we're talking about storage configurations. Immediately, my mind jumps to the specifics – yes, absolutely, we need to consider both `MD_RAID1` and `MD_RAID10`. Those are critical. Now, before going further, let's verify that the kernel supports NVMe target functionality, which is critical for some of the higher-performance solutions that we would recommend. Let's verify `CONFIG_NVME_TARGET`.

28/2 2026/07/23 21:34 tool grepper
0m Args: 
{
  "Expression": "config NVME_TARGET"
}

Results: 
{
  "Output": "drivers/nvme/target/Kconfig-2-\ndrivers/nvme/target/Kconfig:3:config NVME_TARGET\ndrivers/nvme/target/Kconfig-4-\ttristate \"NVMe Target support\"\n--\ndrivers/nvme/target/Kconfig-19-\ndrivers/nvme/target/Kconfig:20:config NVME_TARGET_DEBUGFS\ndrivers/nvme/target/Kconfig-21-        bool \"NVMe Target debugfs support\"\n--\ndrivers/nvme/target/Kconfig-28-\ndrivers/nvme/target/Kconfig:29:config NVME_TARGET_PASSTHRU\ndrivers/nvme/target/Kconfig-30-\tbool \"NVMe Target Passthrough support\"\n--\ndrivers/nvme/target/Kconfig-40-\ndrivers/nvme/target/Kconfig:41:config NVME_TARGET_LOOP\ndrivers/nvme/target/Kconfig-42-\ttristate \"NVMe loopback device support\"\n--\ndrivers/nvme/target/Kconfig-51-\ndrivers/nvme/target/Kconfig:52:config NVME_TARGET_RDMA\ndrivers/nvme/target/Kconfig-53-\ttristate \"NVMe over Fabrics RDMA target support\"\n--\ndrivers/nvme/target/Kconfig-62-\ndrivers/nvme/target/Kconfig:63:config NVME_TARGET_FC\ndrivers/nvme/target/Kconfig-64-\ttristate \"NVMe over Fabrics FC target driver\"\n--\ndrivers/nvme/target/Kconfig-73-\ndrivers/nvme/target/Kconfig:74:config NVME_TARGET_FCLOOP\ndrivers/nvme/target/Kconfig-75-\ttristate \"NVMe over Fabrics FC Transport Loopback Test driver\"\n--\ndrivers/nvme/target/Kconfig-86-\ndrivers/nvme/target/Kconfig:87:config NVME_TARGET_TCP\ndrivers/nvme/target/Kconfig-88-\ttristate \"NVMe over Fabrics TCP target support\"\n--\ndrivers/nvme/target/Kconfig-96-\ndrivers/nvme/target/Kconfig:97:config NVME_TARGET_TCP_TLS\ndrivers/nvme/target/Kconfig-98-\tbool \"NVMe over Fabrics TCP target TLS encryption support\"\n--\ndrivers/nvme/target/Kconfig-109-\ndrivers/nvme/target/Kconfig:110:config NVME_TARGET_AUTH\ndrivers/nvme/target/Kconfig-111-\tbool \"NVMe over Fabrics In-band Authentication in target side\"\n--\ndrivers/nvme/target/Kconfig-119-\ndrivers/nvme/target/Kconfig:120:config NVME_TARGET_AUTH_DEBUG\ndrivers/nvme/target/Kconfig-121-\tbool \"NVMe over Fabrics In-band Authentication debug messages\"\n--\ndrivers/nvme/target/Kconfig-128-\ndrivers/nvme/target/Kconfig:129:config NVME_TARGET_PCI_EPF\ndrivers/nvme/target/Kconfig-130-\ttristate \"NVMe PCI Endpoint Function target support\"\n"
}
29/2 2026/07/23 21:34 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 27734
							output: 279
							thoughts: 456

Thoughts: 
**My Assessment of the Patch's Coverage**

Alright, `NVME_TARGET` alone seems like it should be enough to capture the core changes introduced here. My initial thought process is focusing on the configurations this patch impacts: `MD_RAID1`, `MD_RAID10`, `NVME_RDMA`, `PCI_P2PDMA`, and `NVME_TARGET`. 

I need to make sure I haven't missed any crucial functions. After reviewing, `md_submit_bio` has been touched, but the change sets `REQ_NOMERGE` for P2PDMA bios. Since it is in a hot path, I think I'll skip it to avoid any fuzzing skew. `raid1_write_error` is new, definitely include it. `narrow_write_error` is modified to ensure P2PDMA retry bios remain unmergeable, this is important for coverage. `handle_write_finished` and `handle_write_completed` are modified to address `BLK_STS_P2PDMA` by setting badblocks, which is distinct from a narrow write error, so these are key functions. `handle_read_error` has been modified to block bios if `BLK_STS_P2PDMA`. `nvme_rdma_dma_map_req` uses `ib_dma_map_sgtable_attrs` so it is important to include. Finally, `nvme_rdma_queue_rq` is modified to handle `-EREMOTEIO` by returning `BLK_STS_P2PDMA`.

The overall logic of the patch involves handling `BLK_STS_P2PDMA` errors that surface in the block layer, MD RAID, and NVMe RDMA. In MD RAID, these changes correct the handling of P2PDMA mapping failures by setting badblocks or blocking read requests instead of flagging the underlying device as faulty. NVMe RDMA modifications involve using `ib_dma_map_sgtable_attrs` and returning `BLK_STS_P2PDMA` on mapping failures. Functionally, these changes are relevant to virtualized environments, where NVMe targets can be configured with P2P memory backed by MD arrays, or NVMe RDMA used over software RDMA devices.

I think I've got a good handle on things. Time to call the `set-results` tool.

30/2 2026/07/23 21:34 tool set-results
0m Args: 
{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA",
    "NVME_TARGET"
  ],
  "FocusSymbols": [
    "raid1_write_error",
    "narrow_write_error",
    "handle_write_finished",
    "handle_write_completed",
    "handle_read_error",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch introduces handling for BLK_STS_P2PDMA errors in the block layer, MD RAID (RAID1/RAID10), and NVMe RDMA. It modifies error handling paths in MD RAID to properly handle P2PDMA mapping failures by setting badblocks or blocking reads instead of failing the underlying device. It also modifies NVMe RDMA to use ib_dma_map_sgtable_attrs and return BLK_STS_P2PDMA on mapping failures. These changes are functionally reachable in virtualized environments by configuring NVMe targets with P2P memory backed by MD arrays, or by using NVMe RDMA over software RDMA devices.",
  "WorthFuzzing": true
}

Results: 
{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA",
    "NVME_TARGET"
  ],
  "FocusSymbols": [
    "raid1_write_error",
    "narrow_write_error",
    "handle_write_finished",
    "handle_write_completed",
    "handle_read_error",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch introduces handling for BLK_STS_P2PDMA errors in the block layer, MD RAID (RAID1/RAID10), and NVMe RDMA. It modifies error handling paths in MD RAID to properly handle P2PDMA mapping failures by setting badblocks or blocking reads instead of failing the underlying device. It also modifies NVMe RDMA to use ib_dma_map_sgtable_attrs and return BLK_STS_P2PDMA on mapping failures. These changes are functionally reachable in virtualized environments by configuring NVMe targets with P2P memory backed by MD arrays, or by using NVMe RDMA over software RDMA devices.",
  "WorthFuzzing": true
}
LLM Calls Summary:
Total Calls Total Tokens Avg Tokens Total Duration (Seconds) Avg Duration (Seconds)
Tool Calls Summary:
Total Calls Total Duration (Seconds) Avg Duration (Seconds)