xfs: introduce XFS_SB_LOG_RES() for transactions that modify sb on disk

Introduce a new transaction space reservation XFS_SB_LOG_RES() for
those transactions that need to modify the superblock on disk.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
CC: Dave Chinner <david@fromorbit.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index b46009d..2e30a9a 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -45,6 +45,7 @@
 	uint	tr_qm_dqalloc;	/* allocate quota on disk */
 	uint	tr_qm_quotaoff;	/* turn quota off */
 	uint	tr_qm_equotaoff;/* end of turn quota off */
+	uint	tr_sb;		/* modify superblock */
 } xfs_trans_reservations_t;
 
 #ifndef __KERNEL__