xfs: calculate xfs_qm_write_sb_changes() space log reservation at mount time

For the transaction that write the incore superblock changes of quota flags
to disk, it would reserve the same log space to clear/reset quota flags
transaction, hence we can use XFS_TRANS_SBCHANGE_LOG_RES() for it as well.
Signed-off-by: NJie Liu <jeff.liu@oracle.com>
CC: Dave Chinner <david@fromorbit.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fs/xfs/xfs_qm.c

@@ -1584,10 +1584,9 @@ xfs_qm_write_sb_changes(
 	int		error;
 
 	tp = xfs_trans_alloc(mp, XFS_TRANS_QM_SBCHANGE);
-	if ((error = xfs_trans_reserve(tp, 0,
-				      mp->m_sb.sb_sectsize + 128, 0,
-				      0,
-				      XFS_DEFAULT_LOG_COUNT))) {
+	error = xfs_trans_reserve(tp, 0, XFS_QM_SBCHANGE_LOG_RES(mp),
+				  0, 0, XFS_DEFAULT_LOG_COUNT);
+	if (error) {
 		xfs_trans_cancel(tp, 0);
 		return error;
 	}