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_trans.c b/fs/xfs/xfs_trans.c
index 84643fa..72da2aa 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -606,6 +606,17 @@
 }
 
 /*
+ * Syncing the incore super block changes to disk.
+ *     the super block to reflect the changes: sector size
+ */
+STATIC uint
+xfs_calc_sb_reservation(
+	struct xfs_mount	*mp)
+{
+	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize);
+}
+
+/*
  * Initialize the precomputed transaction reservation values
  * in the mount structure.
  */
@@ -641,6 +652,7 @@
 	resp->tr_qm_dqalloc = xfs_calc_qm_dqalloc_reservation(mp);
 	resp->tr_qm_quotaoff = xfs_calc_qm_quotaoff_reservation(mp);
 	resp->tr_qm_equotaoff = xfs_calc_qm_quotaoff_end_reservation(mp);
+	resp->tr_sb = xfs_calc_sb_reservation(mp);
 }
 
 /*