[PATCH v3 0/2] pnfs/blocklayout: report LAYOUTCOMMIT failures

[Benjamin Coddington <ben.coddington@hammerspace.com>]

From: Benjamin Coddington <bcodding@hammerspace.com>

Data a block or SCSI layout client writes into unwritten extents becomes
file data only when a LAYOUTCOMMIT succeeds.  A server that has revoked
the layout answers NFS4ERR_BADLAYOUT, nfs4_layoutcommit_done() ignores
it, and fsync() and close() return 0 for data that reads back as
zeroes.  nfsd reaches this through its recall failure path today, and
the layout recall series [1] makes it more likely.

Patch 1 keeps the extents uncommitted when the LAYOUTCOMMIT fails before
its result is decoded.  Patch 2 records a writeback error when extents go
uncommitted, and has fsync() check for it after the LAYOUTCOMMIT.

Daejun tested the patch 2 approach on v2 in VMs, against an nfsd that
answers a LAYOUTCOMMIT with NFS4ERR_BADLAYOUT; I've only compile-tested
v3.

Changes since v2:
- Patch 1: add Reviewed-by tags.
- Patch 2: leave ->sync alone and check the file's writeback error in
  nfs_file_fsync() after pnfs_sync_inode(), so each fd reports the error
  once and stat() never returns it (Daejun).  This drops the bl_sync()
  move and the raw wb_err read, and Christoph's v2 Reviewed-by.

v2: https://lore.kernel.org/linux-nfs/cover.1792157092.git.bcodding@hammerspace.com/
v1: https://lore.kernel.org/linux-nfs/cover.1792097970.git.bcodding@hammerspace.com/
[1] https://lore.kernel.org/linux-nfs/20261015-nfsd-layout-recall-v3-0-ba3269f8ca22@samsung.com/

Benjamin Coddington (2):
  pnfs/blocklayout: don't mark extents committed after a failed
    LAYOUTCOMMIT
  pnfs/blocklayout: report data lost to a failed LAYOUTCOMMIT

 fs/nfs/blocklayout/blocklayout.c |  3 ++-
 fs/nfs/blocklayout/extent_tree.c | 14 +++++++++++---
 fs/nfs/file.c                    |  3 +++
 3 files changed, 16 insertions(+), 4 deletions(-)


base-commit: a90ee4305c4a5df72c11b31dacfdc76e00fcf78a
-- 
2.53.0