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Achkinazi, Igor f221e79018 nvme-multipath: set BIO_REMAPPED on bios remapped to per-path namespace disks commit `88bac2c1a7` upstream. When nvme_ns_head_submit_bio() remaps a bio from the multipath head to a per-path namespace, bio_set_dev() clears BIO_REMAPPED. The remapped bio is then resubmitted through submit_bio_noacct() which calls bio_check_eod() because BIO_REMAPPED is not set. This races with nvme_ns_remove() which zeroes the per-path capacity before synchronize_srcu(): CPU 0 (IO submission) --------------------- srcu_read_lock() nvme_find_path() -> ns [NVME_NS_READY is set] CPU 1 (namespace removal) ------------------------- clear_bit(NVME_NS_READY) set_capacity(ns->disk, 0) synchronize_srcu() <- blocks CPU 0 (IO submission) --------------------- bio_set_dev(bio, ns->disk->part0) [clears BIO_REMAPPED] submit_bio_noacct(bio) -> bio_check_eod() sees capacity=0 -> bio fails with IO error The SRCU read lock prevents synchronize_srcu() from completing, but does not prevent set_capacity(0) from executing. The bio fails the EOD check before it reaches the NVMe driver, so nvme_failover_req() never gets a chance to redirect it to another path of multipath. IO errors are reported to the application despite another path being available. On older kernels (before commit `0b64682e78` "block: skip unnecessary checks for split bio"), the same race was also reachable through split remainders resubmitted via submit_bio_noacct(). Fix this by setting BIO_REMAPPED after bio_set_dev() in nvme_ns_head_submit_bio(). This skips bio_check_eod() on the per-path device; the EOD check already passed on the multipath head. NVMe per-path namespace devices are always whole disks (bd_partno=0), so the blk_partition_remap() skip also gated by BIO_REMAPPED is a no-op. The flag does not persist across failover and cannot go stale if the namespace geometry changes between attempts: nvme_failover_req() calls bio_set_dev() to redirect the bio back to the multipath head, which clears BIO_REMAPPED. When nvme_requeue_work() resubmits through submit_bio_noacct(), bio_check_eod() runs normally against the current capacity. Same approach as commit `3a905c37c3` ("block: skip bio_check_eod for partition-remapped bios"). Fixes: `a7c7f7b2b6` ("nvme: use bio_set_dev to assign ->bi_bdev") Cc: stable@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Igor Achkinazi <igor.achkinazi@dell.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2026-07-24 15:51:24 +02:00
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README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.