AI Trajectory

null

{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA"
  ],
  "FocusSymbols": [
    "blk_dma_map_iter_start",
    "md_submit_bio",
    "raid1_end_write_request",
    "raid1_write_request",
    "narrow_write_error",
    "handle_write_finished",
    "handle_read_error",
    "raid10_end_write_request",
    "handle_write_completed",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch modifies the handling of P2PDMA (Peer-to-Peer DMA) requests and mapping errors in the block layer, MD RAID1/RAID10, and NVMe RDMA. It changes how mapping failures are reported and handled, ensuring they are not mistaken for device health issues or invalid requests. This is functional core kernel logic that should be fuzzed.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 703b6c95077d74c7b52f83ddac0b896fc1f39c80\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Sat Jul 18 17:07:04 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c\nindex bfdb9ed7074116..2eed06bfe7917b 100644\n--- a/block/blk-mq-dma.c\n+++ b/block/blk-mq-dma.c\n@@ -190,7 +190,15 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,\n \tcase PCI_P2PDMA_MAP_NONE:\n \t\tbreak;\n \tdefault:\n-\t\titer-\u003estatus = BLK_STS_INVAL;\n+\t\t/*\n+\t\t * P2P transfers that the mapping layer cannot support\n+\t\t * report BLK_STS_TARGET, matching dma_map_sgtable()'s\n+\t\t * -EREMOTEIO and the pre-blk_rq_dma_map nvme behavior:\n+\t\t * the failure is a property of this device pairing, so\n+\t\t * it must not be retried on another path (blk_path_error)\n+\t\t * nor be mistaken for an invalid request.\n+\t\t */\n+\t\titer-\u003estatus = BLK_STS_TARGET;\n \t\treturn false;\n \t}\n \ndiff --git a/drivers/md/md.c b/drivers/md/md.c\nindex d1465bcd86c812..3ae4fd4ef38140 100644\n--- a/drivers/md/md.c\n+++ b/drivers/md/md.c\n@@ -451,8 +451,18 @@ 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 could be mergeable again below md, but for P2PDMA\n+\t * bios REQ_NOMERGE is load-bearing: the DMA mapping type of a\n+\t * request is resolved once, from its first segment, so requests\n+\t * must stay single-provider (see __bio_add_page()). Set the flag\n+\t * rather than merely preserve it -- bios built through the\n+\t * bvec-iter path arrive without it.\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..b1abfc89cfc070 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 +24,35 @@\n #include \u003ctrace/events/block.h\u003e\n \n #define MaxSector (~(sector_t)0)\n+\n+/*\n+ * Check if the bio carries PCI P2PDMA (peer device memory) pages. Read\n+ * bi_io_vec directly rather than using bio_first_bvec_all(), which WARNs\n+ * on cloned bios: md routinely handles split clones, which have\n+ * bi_vcnt == 0 but a valid bi_io_vec shared with the parent. P2PDMA and\n+ * host pages must not be mixed within one bio, so the first bvec is\n+ * representative. Only valid before the bio's iterator is consumed:\n+ * bio_has_data() is false at completion time.\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+ * True when a leg bio failed because its P2PDMA pages cannot be DMA-mapped\n+ * to this member (BLK_STS_TARGET from blk_dma_map_iter_start()). Usable at\n+ * completion time, unlike md_bio_is_p2pdma(): leg bios are clones sharing\n+ * the master bio's bvec table, which outlives the leg's end_io, but their\n+ * iterator is consumed by then, so bio_has_data() cannot gate the access.\n+ */\n+static inline bool md_bio_p2pdma_mapping_error(struct bio *bio)\n+{\n+\treturn bio-\u003ebi_status == BLK_STS_TARGET \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.c b/drivers/md/raid1.c\nindex afe2ca96ad8c22..241c2994b6a3f4 100644\n--- a/drivers/md/raid1.c\n+++ b/drivers/md/raid1.c\n@@ -491,7 +491,9 @@ static void raid1_end_write_request(struct bio *bio)\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    !test_bit(WriteMostly, \u0026rdev-\u003eflags) \u0026\u0026\n+\t\t    /* A mapping failure says nothing about device health */\n+\t\t    !md_bio_p2pdma_mapping_error(bio)) {\n \t\t\tmd_error(r1_bio-\u003emddev, rdev);\n \t\t}\n \n@@ -1575,9 +1577,12 @@ 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 rdev \u0026\u0026 test_bit(WriteMostly, \u0026rdev-\u003eflags) \u0026\u0026\n+\t\t    !md_bio_is_p2pdma(bio))\n \t\t\twrite_behind = true;\n \n \t\tr1_bio-\u003ebios[i] = NULL;\n@@ -2514,7 +2519,7 @@ static void fix_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n \t}\n }\n \n-static void narrow_write_error(struct r1bio *r1_bio, int i)\n+static void narrow_write_error(struct r1bio *r1_bio, int i, bool coarse)\n {\n \tstruct mddev *mddev = r1_bio-\u003emddev;\n \tstruct r1conf *conf = mddev-\u003eprivate;\n@@ -2528,6 +2533,12 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)\n \t * It is conceivable that the bio doesn't exactly align with\n \t * blocks.  We must handle this somehow.\n \t *\n+\t * With 'coarse', retry the whole range as one bio and record\n+\t * one bad range if it fails: used when per-block narrowing\n+\t * cannot find a good block (P2PDMA mapping failures fail the\n+\t * whole range identically), while a single retry still tells\n+\t * a since-cleared transient error apart.\n+\t *\n \t * We currently own a reference on the rdev.\n \t */\n \n@@ -2542,9 +2553,12 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)\n \t\tblock_sectors = roundup(1 \u003c\u003c rdev-\u003ebadblocks.shift, lbs);\n \n \tsector = r1_bio-\u003esector;\n-\tsectors = ((sector + block_sectors)\n-\t\t   \u0026 ~(sector_t)(block_sectors - 1))\n-\t\t- sector;\n+\tif (coarse)\n+\t\tsectors = sect_to_write;\n+\telse\n+\t\tsectors = ((sector + block_sectors)\n+\t\t\t   \u0026 ~(sector_t)(block_sectors - 1))\n+\t\t\t- sector;\n \n \twhile (sect_to_write) {\n \t\tstruct bio *wbio;\n@@ -2562,6 +2576,9 @@ 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@@ -2623,7 +2640,20 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)\n \t\t\t * errors.\n \t\t\t */\n \t\t\tfail = true;\n-\t\t\tnarrow_write_error(r1_bio, m);\n+\t\t\tif (md_bio_p2pdma_mapping_error(r1_bio-\u003ebios[m]))\n+\t\t\t\t/*\n+\t\t\t\t * A P2PDMA mapping failure fails the whole\n+\t\t\t\t * range identically, so narrowing block by\n+\t\t\t\t * block cannot find a good block -- but a\n+\t\t\t\t * transient device error also surfaces as\n+\t\t\t\t * BLK_STS_TARGET, so don't assume.  Retry\n+\t\t\t\t * the range once: if it fails, record it in\n+\t\t\t\t * one go; if it succeeds, there was nothing\n+\t\t\t\t * wrong with the medium.\n+\t\t\t\t */\n+\t\t\t\tnarrow_write_error(r1_bio, m, true);\n+\t\t\telse\n+\t\t\t\tnarrow_write_error(r1_bio, m, false);\n \t\t\trdev_dec_pending(conf-\u003emirrors[m].rdev,\n \t\t\t\t\t conf-\u003emddev);\n \t\t}\n@@ -2650,6 +2680,7 @@ 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+\tbool p2pdma_error = md_bio_p2pdma_mapping_error(bio);\n \tstruct mddev *mddev = conf-\u003emddev;\n \tsector_t sector;\n \n@@ -2669,6 +2700,15 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n \t */\n \tif (mddev-\u003ero) {\n \t\tr1_bio-\u003ebios[r1_bio-\u003eread_disk] = IO_BLOCKED;\n+\t} else if (p2pdma_error) {\n+\t\t/*\n+\t\t * The peer pages cannot be DMA-mapped to this member;\n+\t\t * there is nothing to fix on the medium and the member\n+\t\t * is healthy for host I/O: don't charge the read-error\n+\t\t * budget or fail a FailFast member, just keep this leg\n+\t\t * out of the retry.\n+\t\t */\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);\n \t} else {\ndiff --git a/drivers/md/raid10.c b/drivers/md/raid10.c\nindex 0a3cfdd3f5df80..b24429a19254d8 100644\n--- a/drivers/md/raid10.c\n+++ b/drivers/md/raid10.c\n@@ -489,7 +489,9 @@ static void raid10_end_write_request(struct bio *bio)\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    (bio-\u003ebi_opf \u0026 MD_FAILFAST) \u0026\u0026\n+\t\t\t    /* A mapping failure says nothing about device health */\n+\t\t\t    !md_bio_p2pdma_mapping_error(bio)) {\n \t\t\t\tmd_error(rdev-\u003emddev, rdev);\n \t\t\t}\n \n@@ -2786,7 +2788,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10\n \t}\n }\n \n-static void narrow_write_error(struct r10bio *r10_bio, int i)\n+static void narrow_write_error(struct r10bio *r10_bio, int i, bool coarse)\n {\n \tstruct bio *bio = r10_bio-\u003emaster_bio;\n \tstruct mddev *mddev = r10_bio-\u003emddev;\n@@ -2800,6 +2802,12 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)\n \t * It is conceivable that the bio doesn't exactly align with\n \t * blocks.  We must handle this.\n \t *\n+\t * With 'coarse', retry the whole range as one bio and record\n+\t * one bad range if it fails: used when per-block narrowing\n+\t * cannot find a good block (P2PDMA mapping failures fail the\n+\t * whole range identically), while a single retry still tells\n+\t * a since-cleared transient error apart.\n+\t *\n \t * We currently own a reference to the rdev.\n \t */\n \n@@ -2814,9 +2822,12 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)\n \t\tblock_sectors = roundup(1 \u003c\u003c rdev-\u003ebadblocks.shift, lbs);\n \n \tsector = r10_bio-\u003esector;\n-\tsectors = ((r10_bio-\u003esector + block_sectors)\n-\t\t   \u0026 ~(sector_t)(block_sectors - 1))\n-\t\t- sector;\n+\tif (coarse)\n+\t\tsectors = sect_to_write;\n+\telse\n+\t\tsectors = ((r10_bio-\u003esector + block_sectors)\n+\t\t\t   \u0026 ~(sector_t)(block_sectors - 1))\n+\t\t\t- sector;\n \n \twhile (sect_to_write) {\n \t\tstruct bio *wbio;\n@@ -2831,6 +2842,9 @@ 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 +2867,7 @@ 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@@ -2865,17 +2880,28 @@ 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+\tp2pdma_error = md_bio_p2pdma_mapping_error(bio);\n \tbio_put(bio);\n \tr10_bio-\u003edevs[slot].bio = NULL;\n \n \tif (mddev-\u003ero)\n \t\tr10_bio-\u003edevs[slot].bio = IO_BLOCKED;\n-\telse if (!test_bit(FailFast, \u0026rdev-\u003eflags)) {\n+\telse if (p2pdma_error) {\n+\t\t/*\n+\t\t * The peer pages cannot be DMA-mapped to this member;\n+\t\t * there is nothing to fix on the medium and the member\n+\t\t * is healthy for host I/O: don't charge the read-error\n+\t\t * budget or fail a FailFast member, just keep this leg\n+\t\t * out of the retry.\n+\t\t */\n+\t\tr10_bio-\u003edevs[slot].bio = IO_BLOCKED;\n+\t} else if (test_bit(FailFast, \u0026rdev-\u003eflags)) {\n+\t\tmd_error(mddev, rdev);\n+\t} else {\n \t\tfreeze_array(conf, 1);\n \t\tfix_read_error(conf, mddev, r10_bio);\n \t\tunfreeze_array(conf);\n-\t} else\n-\t\tmd_error(mddev, rdev);\n+\t}\n \n \trdev_dec_pending(rdev, mddev);\n \tr10_bio-\u003estate = 0;\n@@ -2945,7 +2971,23 @@ 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\tif (md_bio_p2pdma_mapping_error(bio))\n+\t\t\t\t\t/*\n+\t\t\t\t\t * A P2PDMA mapping failure fails\n+\t\t\t\t\t * the whole range identically, so\n+\t\t\t\t\t * narrowing block by block cannot\n+\t\t\t\t\t * find a good block -- but a\n+\t\t\t\t\t * transient device error also\n+\t\t\t\t\t * surfaces as BLK_STS_TARGET, so\n+\t\t\t\t\t * don't assume.  Retry the range\n+\t\t\t\t\t * once: if it fails, record it in\n+\t\t\t\t\t * one go; if it succeeds, there\n+\t\t\t\t\t * was nothing wrong with the\n+\t\t\t\t\t * medium.\n+\t\t\t\t\t */\n+\t\t\t\t\tnarrow_write_error(r10_bio, m, true);\n+\t\t\t\telse\n+\t\t\t\t\tnarrow_write_error(r10_bio, m, false);\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..b8642cd2fb793f 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 +1481,12 @@ 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.sgl = req-\u003edata_sgl.sg_table.sgl;\n+\tsgt.orig_nents = req-\u003edata_sgl.nents;\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@@ -2026,8 +2027,6 @@ 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 +2038,13 @@ 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 +2064,13 @@ 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/*\n+\t * The DMA layer refused to map peer memory to this device: a\n+\t * property of the pairing, not a path failure.  Match nvme-pci\n+\t * and do not retry (see blk_path_error()).\n+\t */\n+\telse if (err == -EREMOTEIO)\n+\t\tret = BLK_STS_TARGET;\n \telse\n \t\tret = BLK_STS_IOERR;\n \tnvme_cleanup_cmd(rq);\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA"
  ],
  "FocusSymbols": [
    "blk_dma_map_iter_start",
    "md_submit_bio",
    "raid1_end_write_request",
    "raid1_write_request",
    "narrow_write_error",
    "handle_write_finished",
    "handle_read_error",
    "raid10_end_write_request",
    "handle_write_completed",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch modifies the handling of P2PDMA (Peer-to-Peer DMA) requests and mapping errors in the block layer, MD RAID1/RAID10, and NVMe RDMA. It changes how mapping failures are reported and handled, ensuring they are not mistaken for device health issues or invalid requests. This is functional core kernel logic that should be fuzzed.",
  "WorthFuzzing": true
}

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.

For your convenience, here is the diff of the changes:
commit 703b6c95077d74c7b52f83ddac0b896fc1f39c80
Author: syz-cluster <triage@syzkaller.com>
Date:   Sat Jul 18 17:07:04 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index bfdb9ed7074116..2eed06bfe7917b 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -190,7 +190,15 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,
 	case PCI_P2PDMA_MAP_NONE:
 		break;
 	default:
-		iter->status = BLK_STS_INVAL;
+		/*
+		 * P2P transfers that the mapping layer cannot support
+		 * report BLK_STS_TARGET, matching dma_map_sgtable()'s
+		 * -EREMOTEIO and the pre-blk_rq_dma_map nvme behavior:
+		 * the failure is a property of this device pairing, so
+		 * it must not be retried on another path (blk_path_error)
+		 * nor be mistaken for an invalid request.
+		 */
+		iter->status = BLK_STS_TARGET;
 		return false;
 	}
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d1465bcd86c812..3ae4fd4ef38140 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -451,8 +451,18 @@ 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 could be mergeable again below md, but for P2PDMA
+	 * bios REQ_NOMERGE is load-bearing: the DMA mapping type of a
+	 * request is resolved once, from its first segment, so requests
+	 * must stay single-provider (see __bio_add_page()). Set the flag
+	 * rather than merely preserve it -- bios built through the
+	 * bvec-iter path arrive without it.
+	 */
+	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..b1abfc89cfc070 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 +24,35 @@
 #include <trace/events/block.h>
 
 #define MaxSector (~(sector_t)0)
+
+/*
+ * Check if the bio carries PCI P2PDMA (peer device memory) pages. Read
+ * bi_io_vec directly rather than using bio_first_bvec_all(), which WARNs
+ * on cloned bios: md routinely handles split clones, which have
+ * bi_vcnt == 0 but a valid bi_io_vec shared with the parent. P2PDMA and
+ * host pages must not be mixed within one bio, so the first bvec is
+ * representative. Only valid before the bio's iterator is consumed:
+ * bio_has_data() is false at completion time.
+ */
+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);
+}
+
+/*
+ * True when a leg bio failed because its P2PDMA pages cannot be DMA-mapped
+ * to this member (BLK_STS_TARGET from blk_dma_map_iter_start()). Usable at
+ * completion time, unlike md_bio_is_p2pdma(): leg bios are clones sharing
+ * the master bio's bvec table, which outlives the leg's end_io, but their
+ * iterator is consumed by then, so bio_has_data() cannot gate the access.
+ */
+static inline bool md_bio_p2pdma_mapping_error(struct bio *bio)
+{
+	return bio->bi_status == BLK_STS_TARGET && 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.c b/drivers/md/raid1.c
index afe2ca96ad8c22..241c2994b6a3f4 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -491,7 +491,9 @@ static void raid1_end_write_request(struct bio *bio)
 		if (test_bit(FailFast, &rdev->flags) &&
 		    (bio->bi_opf & MD_FAILFAST) &&
 		    /* We never try FailFast to WriteMostly devices */
-		    !test_bit(WriteMostly, &rdev->flags)) {
+		    !test_bit(WriteMostly, &rdev->flags) &&
+		    /* A mapping failure says nothing about device health */
+		    !md_bio_p2pdma_mapping_error(bio)) {
 			md_error(r1_bio->mddev, rdev);
 		}
 
@@ -1575,9 +1577,12 @@ 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 && rdev && test_bit(WriteMostly, &rdev->flags) &&
+		    !md_bio_is_p2pdma(bio))
 			write_behind = true;
 
 		r1_bio->bios[i] = NULL;
@@ -2514,7 +2519,7 @@ static void fix_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 	}
 }
 
-static void narrow_write_error(struct r1bio *r1_bio, int i)
+static void narrow_write_error(struct r1bio *r1_bio, int i, bool coarse)
 {
 	struct mddev *mddev = r1_bio->mddev;
 	struct r1conf *conf = mddev->private;
@@ -2528,6 +2533,12 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)
 	 * It is conceivable that the bio doesn't exactly align with
 	 * blocks.  We must handle this somehow.
 	 *
+	 * With 'coarse', retry the whole range as one bio and record
+	 * one bad range if it fails: used when per-block narrowing
+	 * cannot find a good block (P2PDMA mapping failures fail the
+	 * whole range identically), while a single retry still tells
+	 * a since-cleared transient error apart.
+	 *
 	 * We currently own a reference on the rdev.
 	 */
 
@@ -2542,9 +2553,12 @@ static void narrow_write_error(struct r1bio *r1_bio, int i)
 		block_sectors = roundup(1 << rdev->badblocks.shift, lbs);
 
 	sector = r1_bio->sector;
-	sectors = ((sector + block_sectors)
-		   & ~(sector_t)(block_sectors - 1))
-		- sector;
+	if (coarse)
+		sectors = sect_to_write;
+	else
+		sectors = ((sector + block_sectors)
+			   & ~(sector_t)(block_sectors - 1))
+			- sector;
 
 	while (sect_to_write) {
 		struct bio *wbio;
@@ -2562,6 +2576,9 @@ 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;
 
@@ -2623,7 +2640,20 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
 			 * errors.
 			 */
 			fail = true;
-			narrow_write_error(r1_bio, m);
+			if (md_bio_p2pdma_mapping_error(r1_bio->bios[m]))
+				/*
+				 * A P2PDMA mapping failure fails the whole
+				 * range identically, so narrowing block by
+				 * block cannot find a good block -- but a
+				 * transient device error also surfaces as
+				 * BLK_STS_TARGET, so don't assume.  Retry
+				 * the range once: if it fails, record it in
+				 * one go; if it succeeds, there was nothing
+				 * wrong with the medium.
+				 */
+				narrow_write_error(r1_bio, m, true);
+			else
+				narrow_write_error(r1_bio, m, false);
 			rdev_dec_pending(conf->mirrors[m].rdev,
 					 conf->mddev);
 		}
@@ -2650,6 +2680,7 @@ 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];
+	bool p2pdma_error = md_bio_p2pdma_mapping_error(bio);
 	struct mddev *mddev = conf->mddev;
 	sector_t sector;
 
@@ -2669,6 +2700,15 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 	 */
 	if (mddev->ro) {
 		r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;
+	} else if (p2pdma_error) {
+		/*
+		 * The peer pages cannot be DMA-mapped to this member;
+		 * there is nothing to fix on the medium and the member
+		 * is healthy for host I/O: don't charge the read-error
+		 * budget or fail a FailFast member, just keep this leg
+		 * out of the retry.
+		 */
+		r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;
 	} else if (test_bit(FailFast, &rdev->flags)) {
 		md_error(mddev, rdev);
 	} else {
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0a3cfdd3f5df80..b24429a19254d8 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -489,7 +489,9 @@ static void raid10_end_write_request(struct bio *bio)
 
 			dec_rdev = 0;
 			if (test_bit(FailFast, &rdev->flags) &&
-			    (bio->bi_opf & MD_FAILFAST)) {
+			    (bio->bi_opf & MD_FAILFAST) &&
+			    /* A mapping failure says nothing about device health */
+			    !md_bio_p2pdma_mapping_error(bio)) {
 				md_error(rdev->mddev, rdev);
 			}
 
@@ -2786,7 +2788,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
 	}
 }
 
-static void narrow_write_error(struct r10bio *r10_bio, int i)
+static void narrow_write_error(struct r10bio *r10_bio, int i, bool coarse)
 {
 	struct bio *bio = r10_bio->master_bio;
 	struct mddev *mddev = r10_bio->mddev;
@@ -2800,6 +2802,12 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)
 	 * It is conceivable that the bio doesn't exactly align with
 	 * blocks.  We must handle this.
 	 *
+	 * With 'coarse', retry the whole range as one bio and record
+	 * one bad range if it fails: used when per-block narrowing
+	 * cannot find a good block (P2PDMA mapping failures fail the
+	 * whole range identically), while a single retry still tells
+	 * a since-cleared transient error apart.
+	 *
 	 * We currently own a reference to the rdev.
 	 */
 
@@ -2814,9 +2822,12 @@ static void narrow_write_error(struct r10bio *r10_bio, int i)
 		block_sectors = roundup(1 << rdev->badblocks.shift, lbs);
 
 	sector = r10_bio->sector;
-	sectors = ((r10_bio->sector + block_sectors)
-		   & ~(sector_t)(block_sectors - 1))
-		- sector;
+	if (coarse)
+		sectors = sect_to_write;
+	else
+		sectors = ((r10_bio->sector + block_sectors)
+			   & ~(sector_t)(block_sectors - 1))
+			- sector;
 
 	while (sect_to_write) {
 		struct bio *wbio;
@@ -2831,6 +2842,9 @@ 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 +2867,7 @@ 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;
 
@@ -2865,17 +2880,28 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 	 * frozen.
 	 */
 	bio = r10_bio->devs[slot].bio;
+	p2pdma_error = md_bio_p2pdma_mapping_error(bio);
 	bio_put(bio);
 	r10_bio->devs[slot].bio = NULL;
 
 	if (mddev->ro)
 		r10_bio->devs[slot].bio = IO_BLOCKED;
-	else if (!test_bit(FailFast, &rdev->flags)) {
+	else if (p2pdma_error) {
+		/*
+		 * The peer pages cannot be DMA-mapped to this member;
+		 * there is nothing to fix on the medium and the member
+		 * is healthy for host I/O: don't charge the read-error
+		 * budget or fail a FailFast member, just keep this leg
+		 * out of the retry.
+		 */
+		r10_bio->devs[slot].bio = IO_BLOCKED;
+	} else if (test_bit(FailFast, &rdev->flags)) {
+		md_error(mddev, rdev);
+	} else {
 		freeze_array(conf, 1);
 		fix_read_error(conf, mddev, r10_bio);
 		unfreeze_array(conf);
-	} else
-		md_error(mddev, rdev);
+	}
 
 	rdev_dec_pending(rdev, mddev);
 	r10_bio->state = 0;
@@ -2945,7 +2971,23 @@ 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);
+				if (md_bio_p2pdma_mapping_error(bio))
+					/*
+					 * A P2PDMA mapping failure fails
+					 * the whole range identically, so
+					 * narrowing block by block cannot
+					 * find a good block -- but a
+					 * transient device error also
+					 * surfaces as BLK_STS_TARGET, so
+					 * don't assume.  Retry the range
+					 * once: if it fails, record it in
+					 * one go; if it succeeds, there
+					 * was nothing wrong with the
+					 * medium.
+					 */
+					narrow_write_error(r10_bio, m, true);
+				else
+					narrow_write_error(r10_bio, m, false);
 				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..b8642cd2fb793f 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 +1481,12 @@ 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.sgl = req->data_sgl.sg_table.sgl;
+	sgt.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 =
@@ -2026,8 +2027,6 @@ 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 +2038,13 @@ 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 +2064,13 @@ 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;
+	/*
+	 * The DMA layer refused to map peer memory to this device: a
+	 * property of the pairing, not a path failure.  Match nvme-pci
+	 * and do not retry (see blk_path_error()).
+	 */
+	else if (err == -EREMOTEIO)
+		ret = BLK_STS_TARGET;
 	else
 		ret = BLK_STS_IOERR;
 	nvme_cleanup_cmd(rq);

gemini-3.1-pro-preview

null

null

							input: 7766
							output: 32
							thoughts: 648
						

**Fuzzing Target Identification: P2PDMA Handling in Block Layer, MD RAID, and NVMe RDMA**

Okay, so I've got a patch here that's poking around in some interesting areas, and my expert intuition is tingling. This patch specifically addresses P2PDMA (Peer-to-Peer DMA) request handling, and it touches core components – the block layer, MD (RAID1/RAID10), and NVMe RDMA. That's a juicy target for fuzzing, no doubt. The changes are spread out, modifying: `block/blk-mq-dma.c`, `drivers/md/md.c`, `drivers/md/md.h`, `drivers/md/raid1.c`, `drivers/md/raid10.c`, and `drivers/nvme/host/rdma.c`.

Essentially, it's about refining how mapping errors for P2PDMA are dealt with across these different subsystems. It looks like they're adding specific error handling routines and modifying existing ones to account for these potential P2PDMA mapping failures. Specifically, I see the introduction of `md_bio_is_p2pdma` and `md_bio_p2pdma_mapping_error` in `drivers/md/md.h`, as well as modifications to `md_submit_bio`, `raid1_end_write_request`, `raid10_end_write_request`, and `nvme_rdma_dma_map_req`. I also see changes to `narrow_write_error` for both RAID1 and RAID10.

It's clear that the patch tries to prevent device failures upon P2PDMA mapping errors, which seems like a sensible design goal. This all points to potential for interesting failure modes and edge cases, which is what makes fuzzing so valuable here. Based on this analysis, I've narrowed down the primary functions I'd want to focus on: `md_submit_bio`, `raid1_end_write_request`, `raid1_write_request`, `narrow_write_error`, `handle_write_finished`, `handle_read_error`, `raid10_end_write_request`, `handle_write_completed`, `nvme_rdma_dma_map_req` and `nvme_rdma_queue_rq`.

Before diving in, I need to confirm the required Kconfig options. For MD, it looks like `MD_RAID1` and `MD_RAID10` are essential. For NVMe RDMA, it's `NVME_RDMA`. And, of course, for P2PDMA, `PCI_P2PDMA` is critical. These need to be validated before I go too far. With these checks in place, I can get down to generating some test cases.

{
  "Expression": "config MD_RAID1",
  "PathPrefix": "drivers/md/Kconfig"
}

{
  "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"
}

gemini-3.1-pro-preview

null

null

							input: 9216
							output: 35
							thoughts: 17
						

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

**Analyzing Potential DMA Acceleration**

Okay, so the immediate question I have is whether we can leverage direct memory access (DMA) effectively here. I need to quickly assess the potential for significant performance gains. My initial thought is to dive into the two most promising candidates: `NVME_RDMA` and `PCI_P2PDMA`.

`NVME_RDMA` is the obvious first place to start. If the storage device supports Remote Direct Memory Access, and we can configure our system to utilize it, that could bypass a lot of the traditional data transfer overhead. I need to look into the specifics of the NVMe controller's capabilities and the RDMA implementation on this platform. What are the latency characteristics? What are the limitations in terms of memory registration and addressing?

Then, I'll switch gears and consider `PCI_P2PDMA`. Point-to-point DMA on the PCIe bus *could* offer a fast path for data transfer, assuming the devices are properly configured within the same I/O domain. This is going to depend heavily on the system's topology and the capabilities of the PCIe root complexes and switches. I'll need to examine the PCIe configuration space and potentially trace the data flow to truly understand its feasibility. What kind of bandwidth can we actually expect? Does the system hardware support peer-to-peer transfers, and are there any required software configurations? The devil is always in the details, so I can't assume anything here.

{
  "Expression": "config NVME_RDMA",
  "PathPrefix": "drivers/nvme/host/Kconfig"
}

{
  "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"
}

gemini-3.1-pro-preview

null

null

							input: 9688
							output: 34
							thoughts: 11
						

Okay, here's my attempt at summarizing that thought process, keeping in mind I'm speaking to a fellow expert:

**PCI_P2PDMA Deep Dive**

Alright, time to get my hands dirty. Let's delve into this PCI_P2PDMA situation. No need for fluff, I'm going straight in, assuming everyone knows the basics. I'm thinking, "Let's check" is the starting point. I need to understand the current status, the dependencies, and any potential bottlenecks or issues. Where should I start looking? The registers, the configuration, the interrupt handling? I need to build a mental map of the system and where this module sits within it, the current state of it, and any issues that might be arising. This is going to require a methodical approach. Time to go.

{
  "Expression": "config PCI_P2PDMA",
  "PathPrefix": "drivers/pci/Kconfig"
}

{
  "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"
}

gemini-3.1-pro-preview

null

null

							input: 9998
							output: 40
							thoughts: 58
						

Here's my take on the changes, presented as a summary of my internal thought process:

**Internal Audit of DMA Mapping Iteration Start**

Okay, so I'm looking at these function modifications and the first one that jumps out is `blk_dma_map_iter_start`. My immediate thought is, "Wait, where is this defined? Is it an inline function? My knowledge is that `blk_dma_map_iter_start` is likely in `blk-mq-dma.c`. I need to confirm this quickly; my memory could be off, so I should double-check the source location and then move forward.

{
  "Expression": "blk_dma_map_iter_start",
  "PathPrefix": "block/blk-mq-dma.c"
}

{
  "Output": "block/blk-mq-dma.c=140=static inline void blk_rq_map_iter_init(struct request *rq,\n--\nblock/blk-mq-dma.c-163-\nblock/blk-mq-dma.c:164:static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,\nblock/blk-mq-dma.c-165-\t\tstruct dma_iova_state *state, struct blk_dma_iter *iter,\n--\nblock/blk-mq-dma.c=234=bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,\n--\nblock/blk-mq-dma.c-237-\tblk_rq_map_iter_init(req, \u0026iter-\u003eiter);\nblock/blk-mq-dma.c:238:\treturn blk_dma_map_iter_start(req, dma_dev, state, iter,\nblock/blk-mq-dma.c-239-\t\t\t\t      blk_rq_payload_bytes(req));\n--\nblock/blk-mq-dma.c=349=bool blk_rq_integrity_dma_map_iter_start(struct request *req,\n--\nblock/blk-mq-dma.c-362-\t};\nblock/blk-mq-dma.c:363:\treturn blk_dma_map_iter_start(req, dma_dev, state, iter, len);\nblock/blk-mq-dma.c-364-}\n"
}

gemini-3.1-pro-preview

null

null

							input: 10651
							output: 33
							thoughts: 251
						

**My Mental Roadmap for RAID and NVMe Write Operations**

Okay, let's see, my mind's been churning through some critical parts of the block layer and storage drivers. I'm focusing on the MD (Multiple Device) drivers, especially those handling RAID configurations, and the NVMe (Non-Volatile Memory Express) over RDMA (Remote Direct Memory Access) subsystem.

First, I'm thinking about the entry point, the `md_submit_bio` function. This is the starting gun for block I/O operations in the MD layer. I'm visualizing the data flowing through the RAID algorithms.

Then, I'm zeroing in on RAID1, which is mirroring. I'm mentally tracing the write path: `raid1_write_request` is how the write is initiated, and `raid1_end_write_request` is called when it completes. It also has error handlers; I'm picturing how `narrow_write_error`, and `handle_write_finished` would work, and the role they play in error recovery and completion signaling for write operations within the RAID1 setup. I'm particularly interested in how `handle_read_error` deals with read failures during write operations on RAID1.

Expanding into RAID10, I'm considering `raid10_end_write_request` and `handle_write_completed`. How do these differ from RAID1 in their handling of write completions and the end-to-end write lifecycle, especially given the striping and mirroring combination? I'm trying to see if I can unify the handling or find a specific rationale for their separate existence.

Now, my thoughts are switching gears to NVMe over RDMA. I have to understand the interaction between the host and the remote NVMe device, and how these write operations are initiated and completed. I'm focusing on `nvme_rdma_dma_map_req`, which will handle DMA mapping, and `nvme_rdma_queue_rq`, which will handle the queuing of the request.

Finally, I'm momentarily interrupting myself. Just a quick check... I need to verify whether `narrow_write_error` is declared as a static function. That's just a quick detail, but it could impact the scope and implications of my overall understanding of the error handling strategy.

{
  "Expression": "narrow_write_error",
  "PathPrefix": "drivers/md/raid1.c"
}

{
  "Output": "drivers/md/raid1.c=2437=static void fix_read_error(struct r1conf *conf, struct r1bio *r1_bio)\n--\ndrivers/md/raid1.c-2521-\ndrivers/md/raid1.c:2522:static void narrow_write_error(struct r1bio *r1_bio, int i, bool coarse)\ndrivers/md/raid1.c-2523-{\n--\ndrivers/md/raid1.c=2625=static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)\n--\ndrivers/md/raid1.c-2653-\t\t\t\t */\ndrivers/md/raid1.c:2654:\t\t\t\tnarrow_write_error(r1_bio, m, true);\ndrivers/md/raid1.c-2655-\t\t\telse\ndrivers/md/raid1.c:2656:\t\t\t\tnarrow_write_error(r1_bio, m, false);\ndrivers/md/raid1.c-2657-\t\t\trdev_dec_pending(conf-\u003emirrors[m].rdev,\n"
}

gemini-3.1-pro-preview

null

null

							input: 11726
							output: 253
							thoughts: 515
						

**Analyzing the Scope of a P2PDMA Error Handling Patch**

Okay, so I'm looking at a patch that's clearly focused on improving error handling related to P2PDMA, specifically within the realms of MD RAID (RAID1 and RAID10, it seems) and NVMe RDMA. It's functional, meaning the core logic is sound and the intended change is implemented.

My initial thought was to double-check if the `PCI_P2PDMA` config option is sufficient. It is; it's a simple boolean. No need to muddy the waters with `PCI_P2PDMA_TEST` or anything more complex.

Now, I need to refine the list of focus symbols to provide as targeted a review as possible. The original list is a decent starting point. The entry points, `md_submit_bio` for MD and `nvme_rdma_queue_rq` for NVMe RDMA, are crucial since the patch modifies logic there. `raid1_write_request` and similar functions are key within their respective RAID implementations. The change is precisely within these error-handling paths.

The inclusion of `blk_dma_map_iter_start`, `raid1_end_write_request`, `handle_write_finished`, `handle_read_error`, `raid10_end_write_request`, `handle_write_completed`, `nvme_rdma_dma_map_req`, and `narrow_write_error` rounds out the specific functions that are touched by this patch and clarifies the focus on error-related flows.

{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA"
  ],
  "FocusSymbols": [
    "blk_dma_map_iter_start",
    "md_submit_bio",
    "raid1_end_write_request",
    "raid1_write_request",
    "narrow_write_error",
    "handle_write_finished",
    "handle_read_error",
    "raid10_end_write_request",
    "handle_write_completed",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch modifies the handling of P2PDMA (Peer-to-Peer DMA) requests and mapping errors in the block layer, MD RAID1/RAID10, and NVMe RDMA. It changes how mapping failures are reported and handled, ensuring they are not mistaken for device health issues or invalid requests. This is functional core kernel logic that should be fuzzed.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "MD_RAID1",
    "MD_RAID10",
    "NVME_RDMA",
    "PCI_P2PDMA"
  ],
  "FocusSymbols": [
    "blk_dma_map_iter_start",
    "md_submit_bio",
    "raid1_end_write_request",
    "raid1_write_request",
    "narrow_write_error",
    "handle_write_finished",
    "handle_read_error",
    "raid10_end_write_request",
    "handle_write_completed",
    "nvme_rdma_dma_map_req",
    "nvme_rdma_queue_rq"
  ],
  "Reasoning": "The patch modifies the handling of P2PDMA (Peer-to-Peer DMA) requests and mapping errors in the block layer, MD RAID1/RAID10, and NVMe RDMA. It changes how mapping failures are reported and handled, ensuring they are not mistaken for device health issues or invalid requests. This is functional core kernel logic that should be fuzzed.",
  "WorthFuzzing": true
}