xfs: consolidate superblock logging functions

We now have several superblock loggin functions that are identical
except for the transaction reservation and whether it shoul dbe a
synchronous transaction or not. Consolidate these all into a single
function, a single reserveration and a sync flag and call it
xfs_sync_sb().

Also, xfs_mod_sb() is not really a modification function - it's the
operation of logging the superblock buffer. hence change the name of
it to reflect this.

Note that we have to change the mp->m_update_flags that are passed
around at mount time to a boolean simply to indicate a superblock
update is needed.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 8c39cc8..63a5bb9 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1221,20 +1221,20 @@
 		goto bmap_cancel;
 	if (!xfs_sb_version_hasattr(&mp->m_sb) ||
 	   (!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2)) {
-		bool mod_sb = false;
+		bool log_sb = false;
 
 		spin_lock(&mp->m_sb_lock);
 		if (!xfs_sb_version_hasattr(&mp->m_sb)) {
 			xfs_sb_version_addattr(&mp->m_sb);
-			mod_sb = true;
+			log_sb = true;
 		}
 		if (!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2) {
 			xfs_sb_version_addattr2(&mp->m_sb);
-			mod_sb = true;
+			log_sb = true;
 		}
 		spin_unlock(&mp->m_sb_lock);
-		if (mod_sb)
-			xfs_mod_sb(tp);
+		if (log_sb)
+			xfs_log_sb(tp);
 	}
 
 	error = xfs_bmap_finish(&tp, &flist, &committed);