[XFS] make inode reclaim synchronise with xfs_iflush_done()

On a forced shutdown, xfs_finish_reclaim() will skip flushing the inode.
If the inode flush lock is not already held and there is an outstanding
xfs_iflush_done() then we might free the inode prematurely. By acquiring
and releasing the flush lock we will synchronise with xfs_iflush_done().

SGI-PV: 909874
SGI-Modid: xfs-linux-melb:xfs-kern:30468a
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: David Chinner <dgc@sgi.com>

fs/xfs/xfs_vnodeops.c

@@ -3694,12 +3694,12 @@ xfs_finish_reclaim(
 	 * We get the flush lock regardless, though, just to make sure
 	 * we don't free it while it is being flushed.
 	 */
-	if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
 	if (!locked) {
 		xfs_ilock(ip, XFS_ILOCK_EXCL);
 		xfs_iflock(ip);
 	}
 
+	if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
 		if (ip->i_update_core ||
 		    ((ip->i_itemp != NULL) &&
 		     (ip->i_itemp->ili_format.ilf_fields != 0))) {
@@ -3719,16 +3719,10 @@ xfs_finish_reclaim(
 		ASSERT(ip->i_update_core == 0);
 		ASSERT(ip->i_itemp == NULL ||
 		       ip->i_itemp->ili_format.ilf_fields == 0);
-		xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	} else if (locked) {
-		/*
-		 * We are not interested in doing an iflush if we're
-		 * in the process of shutting down the filesystem forcibly.
-		 * So, just reclaim the inode.
-		 */
+	}
+
 	xfs_ifunlock(ip);
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
-	}
 
  reclaim:
 	xfs_ireclaim(ip);