4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Chinner <dchin...@redhat.com>

commit 51b07f30a71c27405259a0248206ed4e22adbee2 upstream.

Some careless idiot(*) wrote crap code in commit 1a3e8f3 ("xfs:
convert inode cache lookups to use RCU locking") back in late 2010,
and so xfs_iflush_cluster checks the wrong inode for whether it is
still valid under RCU protection. Fix it to lock and check the
correct inode.

(*) Careless-idiot: Dave Chinner <dchin...@redhat.com>

Discovered-by: Brain Foster <bfos...@redhat.com>
Signed-off-by: Dave Chinner <dchin...@redhat.com>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Dave Chinner <da...@fromorbit.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/xfs/xfs_inode.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3205,13 +3205,13 @@ xfs_iflush_cluster(
                 * We need to check under the i_flags_lock for a valid inode
                 * here. Skip it if it is not valid or the wrong inode.
                 */
-               spin_lock(&ip->i_flags_lock);
-               if (!ip->i_ino ||
+               spin_lock(&iq->i_flags_lock);
+               if (!iq->i_ino ||
                    (XFS_INO_TO_AGINO(mp, iq->i_ino) & mask) != first_index) {
-                       spin_unlock(&ip->i_flags_lock);
+                       spin_unlock(&iq->i_flags_lock);
                        continue;
                }
-               spin_unlock(&ip->i_flags_lock);
+               spin_unlock(&iq->i_flags_lock);
 
                /*
                 * Do an un-protected check to see if the inode is dirty and


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