[added to the 4.1 stable tree] xfs: fix inode validity check in xfs_iflush_cluster

From: Dave Chinner <redacted>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 51b07f30a71c27405259a0248206ed4e22adbee2 ]

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 [off-list ref]

cc: <redacted> # 3.10.x-
Discovered-by: Brain Foster [off-list ref]
Signed-off-by: Dave Chinner <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Sasha Levin <redacted>
---
 fs/xfs/xfs_inode.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index e395a5c..c9f8637 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c

@@ -3236,13 +3236,13 @@ 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

-- 
2.5.0