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xfs: always succeed at setting the reserve pool size

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commit 0baa2657dc4d79202148be79a3dc36c35f425060 upstream.

Nowadays, xfs_mod_fdblocks will always choose to fill the reserve pool
with freed blocks before adding to fdblocks.  Therefore, we can change
the behavior of xfs_reserve_blocks slightly -- setting the target size
of the pool should always succeed, since a deficiency will eventually
be made up as blocks get freed.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Darrick J. Wong
2022-09-01 16:33:53 +03:00
committed by Greg Kroah-Hartman
parent cb41f22df3
commit 72a259bdd5
1 changed files with 5 additions and 4 deletions
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9
fs/xfs/xfs_fsops.c
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@@ -380,11 +380,14 @@ xfs_reserve_blocks(
* The code below estimates how many blocks it can request from * The code below estimates how many blocks it can request from
* fdblocks to stash in the reserve pool. This is a classic TOCTOU * fdblocks to stash in the reserve pool. This is a classic TOCTOU
* race since fdblocks updates are not always coordinated via * race since fdblocks updates are not always coordinated via
* m_sb_lock. * m_sb_lock. Set the reserve size even if there's not enough free
* space to fill it because mod_fdblocks will refill an undersized
* reserve when it can.
*/ */
free = percpu_counter_sum(&mp->m_fdblocks) - free = percpu_counter_sum(&mp->m_fdblocks) -
xfs_fdblocks_unavailable(mp); xfs_fdblocks_unavailable(mp);
delta = request - mp->m_resblks; delta = request - mp->m_resblks;
mp->m_resblks = request;
if (delta > 0 && free > 0) { if (delta > 0 && free > 0) {
/* /*
* We'll either succeed in getting space from the free block * We'll either succeed in getting space from the free block
@@ -401,10 +404,8 @@ xfs_reserve_blocks(
* Update the reserve counters if blocks have been successfully * Update the reserve counters if blocks have been successfully
* allocated. * allocated.
*/ */
if (!error) { if (!error)
mp->m_resblks += fdblks_delta;
mp->m_resblks_avail += fdblks_delta; mp->m_resblks_avail += fdblks_delta;
}
} }
out: out:
if (outval) { if (outval) {