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xfs: take the invalidate lock while mapping a pNFS layout

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xfs_fs_map_blocks() flushes the page cache under the iolock, but a
write fault takes only the invalidate lock. A fault on a shared mapping
can then add a delalloc extent before the range is mapped. That trips
an ASSERT, or nfsd warns and refuses the layout.

Take the invalidate lock with the iolock, as __xfs_file_fallocate()
does. Not for stable: pNFS already leaves local writers to shared
mappings unsynchronized.

Suggested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20260519145949.GH9555@frogsfrogsfrogs
Signed-off-by: Daejun Park <daejun7.park@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
This commit is contained in:
Daejun Park 2026-10-29 11:23:04 +09:00 committed by Carlos Maiolino
parent 29f3c1be4e
commit 23ba20ef28
1 changed files with 6 additions and 3 deletions
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9
fs/xfs/xfs_pnfs.c
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@ -168,8 +168,11 @@ xfs_fs_map_blocks(
* similar to direct I/O, except that the synchronization is much more
* complicated. See the comment near xfs_break_leased_layouts
* for a detailed explanation.
*
* Take the invalidate lock as well, so that page faults cannot add
* delalloc extents to the range while it is being mapped.
*/
xfs_ilock(ip, XFS_IOLOCK_EXCL);
xfs_ilock(ip, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
error = -EINVAL;
limit = mp->m_super->s_maxbytes;
@ -251,13 +254,13 @@ xfs_fs_map_blocks(
if (error)
goto out_unlock;
}
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
xfs_iunlock(ip, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0, 0, seq);
*device_generation = mp->m_generation;
return error;
out_unlock:
xfs_iunlock(ip, XFS_IOLOCK_EXCL);
xfs_iunlock(ip, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
return error;
}