xfs: fix racy open zone caching

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When testing on very fast storage devices, I've observed writers using
io_uring creating many open zones with just a few kiB written to it,
which then don't get used.  I tracked this down to multiple io_uring
helper threads finding a full zone in i_private, and then going on to
select a one, with the final one winning the race and leaving it in
i_private.

Fix this by dropping full zones from i_private as soon we find them,
checking cached for a cached zoned when a single writes needs a new zone,
and by keeping an existing cached zone in xfs_set_cached_zone when it
still has space available, dropping the newly found/allocated one
instead.  This uses i_flags_lock as a low-level spinlock for short
hold times to avoid interactions with the ilock, which is used for
completions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

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This commit is contained in:

Christoph Hellwig 2026-08-11 10:48:38 -06:00 • committed by Carlos Maiolino

parent ae28561189

commit 2d829cc767

1 changed files with 53 additions and 13 deletions

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fs/xfs/xfs_zone_alloc.c

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