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xfs: always succeed at setting the reserve pool size 

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>
This commit is contained in:
Darrick J. Wong 2022-03-24 12:43:32 -07:00
parent 15f04fdc75
commit 0baa2657dc
1 changed files with 5 additions and 4 deletions
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9
fs/xfs/xfs_fsops.c
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@ -434,11 +434,14 @@ xfs_reserve_blocks(
* The code below estimates how many blocks it can request from
* fdblocks to stash in the reserve pool. This is a classic TOCTOU
* 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) -
xfs_fdblocks_unavailable(mp);
delta = request - mp->m_resblks;
mp->m_resblks = request;
if (delta > 0 && free > 0) {
/*
* We'll either succeed in getting space from the free block
@ -455,11 +458,9 @@ xfs_reserve_blocks(
* Update the reserve counters if blocks have been successfully
* allocated.
*/
if (!error) {
mp->m_resblks += fdblks_delta;
if (!error)
mp->m_resblks_avail += fdblks_delta;
}
}
out:
if (outval) {
outval->resblks = mp->m_resblks;