[XFS] Really fix use after free in xfs_iunpin.

The previous attempts to fix the linux inode use-after-free in xfs_iunpin
simply made the problem harder to hit. We actually need complete exclusion
between xfs_reclaim and xfs_iunpin, as well as ensuring that the i_flags
are consistent during both of these functions. Introduce a new spinlock
for exclusion and the i_flags, and fix up xfs_iunpin to use igrab before
marking the inode dirty.

SGI-PV: 952967
SGI-Modid: xfs-linux-melb:xfs-kern:26964a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
index b608b8ab1dd6..136c6b06f1c9 100644
--- a/fs/xfs/xfs_itable.c
+++ b/fs/xfs/xfs_itable.c
@@ -577,6 +577,7 @@ xfs_bulkstat(
                                                                       KM_SLEEP);
                                                 ip->i_ino = ino;
                                                 ip->i_mount = mp;
+                                                spin_lock_init(&ip->i_flags_lock);
                                                 if (bp)
                                                         xfs_buf_relse(bp);
                                                 error = xfs_itobp(mp, NULL, ip,