block,md,nvme: correct handling of unsupported P2PDMA transfers - #26
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block,md,nvme: correct handling of unsupported P2PDMA transfers#26blktests-ci-block-trial[bot] wants to merge 8 commits into
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Unsupported P2P transfers used to fail with BLK_STS_TARGET, chosen by commit 91fb2b6 ("nvme-pci: convert to using dma_map_sgtable()") for dma_map_sgtable()'s -EREMOTEIO: an I/O that can never succeed on this device must not be retried. The blk_rq_dma_map conversion changed it to BLK_STS_INVAL, which blk_path_error() treats as retryable and md deliberately ignores for member failures -- a P2P write to a member the peer cannot reach is counted as written and the mirrors silently diverge. Restore BLK_STS_TARGET. Hit e.g. with CMB memory of one NVMe device used as the data buffer for I/O to a second one behind a different host bridge. Fixes: 858299d ("block: add scatterlist-less DMA mapping helpers") Fixes: 7ce3c1d ("nvme-pci: convert the data mapping to blk_rq_dma_map") Cc: stable@vger.kernel.org # v6.17 Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
md_submit_bio() strips REQ_NOMERGE from every bio. For P2PDMA bios the flag is what keeps requests single-provider (see __bio_add_page()): merging a P2PDMA bio with one over a different pgmap, or over host memory, maps the merged request with the wrong bus address. Set the flag on P2PDMA bios -- bios built via bio_iov_bvec_set() arrive without it -- and keep stripping it otherwise. Fixes: 0266613 ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
A write that skips write-behind (full behind queue, a waiting reader, failed behind-bio allocation) races the in-flight behind write it overlaps: nothing orders the two on the write-mostly member, and if the older behind data lands last the member keeps stale data for sectors already acknowledged as rewritten. Serialize on CollisionCheck, which marks exactly the rdevs owning a serial tree: serialize_policy rdevs plus write-mostly members when write-behind arms serialization -- the case the MD_SERIALIZE_POLICY test misses. remove_serial() under the same condition. This also avoids the old gate's latent NULL deref for rdevs hot-added under serialize_policy (they never get a serial tree). Fixes: d0d2d8b ("md/raid1: introduce wait_for_serialization") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-fable-5 Signed-off-by: Mykola Marzhan <mykola@meshstor.io>
alloc_behind_master_bio() copies the bio's data with bio_copy_data(), a CPU copy. P2PDMA pages are peer device (BAR) memory; generic code must not assume CPU load/store access to them is safe or fast on every architecture, and bouncing peer memory through the CPU defeats the point of a peer-to-peer transfer. Skip write-behind for P2PDMA bios: they are written directly to all members, including write-mostly ones. Ordering against write-behind I/O in flight to overlapping sectors is preserved: the non-behind clone path serializes on CollisionCheck rdevs (see the preceding fix), which covers these bios like any other write that bypasses write-behind. Fixes: 0266613 ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
narrow_write_error() re-issues a failed write in badblock-granularity chunks, cloning from the master bio and resetting bi_opf to a bare REQ_OP_WRITE. For a P2PDMA bio that reset drops REQ_NOMERGE, which is the only request-level protection against the member queue merging P2PDMA segments across pgmaps or with host memory (see the preceding md_submit_bio() fix): the retry path would quietly reopen the hole the submission path closes. Restore the flag on P2PDMA retry clones. Fixes: 0266613 ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
A member that cannot DMA-map peer memory fails the leg bio with BLK_STS_TARGET. The failure is a property of the peer/member pairing -- retrying the same pages against the same member cannot succeed, and there is nothing on the medium to repair -- but the error machinery treats it as a medium error: narrow_write_error() grinds through hundreds of doomed chunk retries per write, WantReplacement burns a spare and evicts the healthy member, fix_read_error()'s host-page probe "succeeds" so mixed host/P2P reads charge the read-error budget until a healthy member is kicked (~1s in testing), and FailFast evicts on the first unroutable I/O. Flag P2PDMA master bios with a new R1BIO_P2PDMA state bit at submission. On a BLK_STS_TARGET leg failure for a flagged bio: retry writes once as a single whole range, recording one bad range if that also fails (TARGET can be a transient device condition, e.g. NVME_SC_NS_NOT_READY, so the retry is not skipped outright); don't set WantReplacement; mark failed read legs IO_BLOCKED without charging the read-error budget; and don't treat the failure as FailFast evidence -- the request never reached the wire -- as commit f7b24c7 ("md/raid1,raid10: don't fail devices for invalid IO errors") did for BLK_STS_INVAL. Fixes: 0266613 ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io>
Same handling as the preceding raid1 commit: flag P2PDMA master bios with R10BIO_P2PDMA at submission; on a BLK_STS_TARGET leg failure retry writes once as a whole range, don't set WantReplacement, block the leg for reads without charging the read-error budget, don't trip FailFast. Replacement legs keep the stock fail-on-write-error policy: badblocks are never recorded on a replacement, so failing it is the only outcome that cannot leave a silent hole in a rebuild. Fixes: 0266613 ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Mykola Marzhan <mykola@meshstor.io>
ib_dma_map_sg() returns 0 on a P2P mapping failure, losing the DMA layer's -EREMOTEIO, so nvme-rdma reports a path error. Default multipath requeues the I/O forever, and without multipath it burns nvme_max_retries requeues, then completes as retryable BLK_STS_TRANSPORT. Map the data and metadata scatterlists with ib_dma_map_sgtable_attrs() and return BLK_STS_TARGET for -EREMOTEIO, matching nvme-pci (commit 91fb2b6 ("nvme-pci: convert to using dma_map_sgtable()")). Scatterlists stay: ib_map_mr_sg() consumes them, so blk_rq_dma_map does not apply. Start the request only after mapping succeeds so multipath accounting is never taken for an unmapped request, and ratelimit the map-failure message. Fixes: 23528aa ("nvme: enable PCI P2PDMA support for RDMA transport") Cc: stable@vger.kernel.org # v7.1 Assisted-by: Claude:claude-fable-5 Signed-off-by: Mykola Marzhan <mykola@meshstor.io>
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Pull request for series with
subject: block,md,nvme: correct handling of unsupported P2PDMA transfers
version: 3
url: http://redsun45:8000/project/linux-block/list/?series=399