[PATCH] xfs: unregister inode shrinker before freeing filesystem structures

[Dave Chinner]

From: Dave Chinner <dchinner at redhat.com>

Currently we don't remove the XFS mount from the shrinker list until late in
the unmount path. By this time, we have already torn down the internals of the
filesystem (e.g. the per-ag structures), and hence if the shrinker is executed
between the teardown and the unregistering, the shrinker will get NULL per-ag
structure pointers and panic trying to dereference them.

Fix this by removingthe xfs mount from the shrinker list before tearing down
it's internal structures.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
---
 fs/xfs/linux-2.6/xfs_super.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index e3de46c..4605cd4 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1156,9 +1156,13 @@ xfs_fs_put_super(
 
 	XFS_bflush(mp->m_ddev_targp);
 
+	/*
+	 * Unregister the memory shrinker before we tear down the mount
+	 * structure so we don't have memory reclaim racing with us here.
+	 */
+	xfs_inode_shrinker_unregister(mp);
 	xfs_unmountfs(mp);
 	xfs_freesb(mp);
-	xfs_inode_shrinker_unregister(mp);
 	xfs_icsb_destroy_counters(mp);
 	xfs_close_devices(mp);
 	xfs_free_fsname(mp);
-- 
1.7.1