[PATCH v3 0/4] iomap: fix error handling regressions

[Andrea Parri]

Fix three independent error handling regressions in iomap:

 - clear the writeback context after a failed ->writeback_submit() call,
   preventing an already completed ioend from being submitted again;
 - preserve an iomap iteration error when iomap_fiemap() has a pending
   extent to emit; and
 - preserve a direct I/O data path error when sub-block tail zeroing
   succeeds.

The three fixes have no ordering dependencies and can be applied or
backported independently.  Each issue was reproduced before and after
its respective fix.

Patch 2 is not a fix and carries no stable tag: it adds an XFS error
tag (requested by Christoph) that lets patch 1's ->writeback_submit()
failure be injected without the boot-param hack used for the original
reproduction.  The corresponding xfstest (list corruption caught via
CONFIG_LIST_HARDENED on an unfixed kernel, clean writeback failure on a
fixed one) was posted to fstests@xxxxxxxxxxxxxxx:

  https://lore.kernel.org/all/20260924091338.198407-1-parri.andrea@xxxxxxxxx/

Changes since v2:
 - Patch 1: no code change; picked up Christoph's Reviewed-by.
 - Patch 2: fixed the alignment of the new XFS_ERRTAG_WB_COW_CONVERT_ERROR
   define; picked up Reviewed-by tags from Darrick and Christoph.
 - Patch 3: no change.
 - Patch 4: dropped the reformatting of the iomap_dio_zero() prototype,
   keeping the iomap two-tab indent style (Christoph); added the
   "# v6.12" stable version tag (Darrick); picked up Reviewed-by tags
   from Darrick and Pankaj.

Changes since v1:
 - Patch 1: reworded the added comment to fit 80 columns (Christoph);
   described the reproducer in the commit message (fault-injected
   ->writeback_submit() failure on a reflinked XFS file, reliably hits
   list_add double add on the unfixed kernel); documented why the final
   ->writeback_submit() call in iomap_writepages() needs no equivalent
   fix, since wpc is never reused after it; picked up the version-scoped
   stable tag Darrick suggested; picked up Brian's Reviewed-by.
 - Patch 2: new, added per Christoph's request.
 - Patch 3 (was 2/3): no code change; picked up the version-scoped
   stable tag Darrick suggested; picked up Reviewed-by tags from Brian,
   Darrick, and Christoph.
 - Patch 4 (was 3/3): reworked per Christoph's suggestion to make
   iomap_dio_zero() return void and drop the handling of its return
   value, since it can only fail via a can't-happen WARN_ON_ONCE()
   assert; this also resolves Darrick's question about the local
   variable's type.  Brian's v1 Reviewed-by was dropped due to the
   rework.

v2: https://lore.kernel.org/all/20260924091203.198225-1-parri.andrea@xxxxxxxxx/
v1: https://lore.kernel.org/all/20260921083133.2960-1-parri.andrea@xxxxxxxxx/

Andrea Parri (4):
  iomap: don't resubmit an ioend after ->writeback_submit() failed
  xfs: add an error tag to inject a ->writeback_submit() failure
  iomap: don't lose a fiemap iteration error when emitting the last
    extent
  iomap: don't lose a failed direct I/O bio's error when zeroing the
    tail

 fs/iomap/direct-io.c         | 16 +++++-----------
 fs/iomap/fiemap.c            |  8 ++++----
 fs/iomap/ioend.c             | 10 +++++++++-
 fs/xfs/libxfs/xfs_errortag.h |  6 ++++--
 fs/xfs/xfs_reflink.c         |  5 +++++
 5 files changed, 27 insertions(+), 18 deletions(-)


base-commit: 93f51579e7df248780214094418f205253383cc5
-- 
2.53.0