Commit 081003ff authored Oct 01, 2010 by Johannes Weiner Committed by Alex Elder Oct 06, 2010

xfs: properly account for reclaimed inodes



When marking an inode reclaimable, a per-AG counter is increased, the
inode is tagged reclaimable in its per-AG tree, and, when this is the
first reclaimable inode in the AG, the AG entry in the per-mount tree
is also tagged.

When an inode is finally reclaimed, however, it is only deleted from
the per-AG tree.  Neither the counter is decreased, nor is the parent
tree's AG entry untagged properly.

Since the tags in the per-mount tree are not cleared, the inode
shrinker iterates over all AGs that have had reclaimable inodes at one
point in time.

The counters on the other hand signal an increasing amount of slab
objects to reclaim.  Since "70e60ce7 xfs: convert inode shrinker to
per-filesystem context" this is not a real issue anymore because the
shrinker bails out after one iteration.

But the problem was observable on a machine running v2.6.34, where the
reclaimable work increased and each process going into direct reclaim
eventually got stuck on the xfs inode shrinking path, trying to scan
several million objects.

Fix this by properly unwinding the reclaimable-state tracking of an
inode when it is reclaimed.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@kernel.org
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

parent 7c6d45e6

fs/xfs/linux-2.6/xfs_sync.c

+14 −5

Original line number	Diff line number	Diff line
		@@ -668,14 +668,11 @@ xfs_inode_set_reclaim_tag(
		xfs_perag_put(pag);
		}

		void
		__xfs_inode_clear_reclaim_tag(
		xfs_mount_t *mp,
		STATIC void
		__xfs_inode_clear_reclaim(
		xfs_perag_t *pag,
		xfs_inode_t *ip)
		{
		radix_tree_tag_clear(&pag->pag_ici_root,
		XFS_INO_TO_AGINO(mp, ip->i_ino), XFS_ICI_RECLAIM_TAG);
		pag->pag_ici_reclaimable--;
		if (!pag->pag_ici_reclaimable) {
		/* clear the reclaim tag from the perag radix tree */
		@@ -689,6 +686,17 @@ __xfs_inode_clear_reclaim_tag(
		}
		}

		void
		__xfs_inode_clear_reclaim_tag(
		xfs_mount_t *mp,
		xfs_perag_t *pag,
		xfs_inode_t *ip)
		{
		radix_tree_tag_clear(&pag->pag_ici_root,
		XFS_INO_TO_AGINO(mp, ip->i_ino), XFS_ICI_RECLAIM_TAG);
		__xfs_inode_clear_reclaim(pag, ip);
		}

		/*
		* Inodes in different states need to be treated differently, and the return
		* value of xfs_iflush is not sufficient to get this right. The following table
		@@ -838,6 +846,7 @@ reclaim:
		if (!radix_tree_delete(&pag->pag_ici_root,
		XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino)))
		ASSERT(0);
		__xfs_inode_clear_reclaim(pag, ip);
		write_unlock(&pag->pag_ici_lock);

		/*

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