[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_inode.h b/fs/xfs/xfs_inode.h
index fdb89f72db9..e96eb0835fe 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -267,6 +267,7 @@ typedef struct xfs_inode {
         sema_t                  i_flock;        /* inode flush lock */
         atomic_t                i_pincount;     /* inode pin count */
         wait_queue_head_t       i_ipin_wait;    /* inode pinning wait queue */
+        spinlock_t              i_flags_lock;   /* inode i_flags lock */
 #ifdef HAVE_REFCACHE
         struct xfs_inode        **i_refcache;   /* ptr to entry in ref cache */
         struct xfs_inode        *i_release;     /* inode to unref */