Commit 0baa2657 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

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: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent 15f04fdc

fs/xfs/xfs_fsops.c

+5 −4
Original line number Diff line number Diff line
@@ -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;