[GFS2] Fix incorrect fs sync behaviour.

This adds a sync_fs superblock operation for GFS2 and removes
the journal flush from write_super in favour of sync_fs where it
ought to be. This is more or less identical to the way in which ext3
does this.

This bug was pointed out by Russell Cattelan <cattelan@redhat.com>

Cc: Russell Cattelan <cattelan@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/ops_super.c

@@ -138,16 +138,27 @@ static void gfs2_put_super(struct super_block *sb)
 }
 
 /**
- * gfs2_write_super - disk commit all incore transactions
- * @sb: the filesystem
+ * gfs2_write_super
+ * @sb: the superblock
  *
- * This function is called every time sync(2) is called.
- * After this exits, all dirty buffers are synced.
  */
 
 static void gfs2_write_super(struct super_block *sb)
 {
+	sb->s_dirt = 0;
+}
+
+/**
+ * gfs2_sync_fs - sync the filesystem
+ * @sb: the superblock
+ *
+ * Flushes the log to disk.
+ */
+static int gfs2_sync_fs(struct super_block *sb, int wait)
+{
+	sb->s_dirt = 0;
 	gfs2_log_flush(sb->s_fs_info, NULL);
+	return 0;
 }
 
 /**
@@ -458,6 +469,7 @@ struct super_operations gfs2_super_ops = {
 	.delete_inode		= gfs2_delete_inode,
 	.put_super		= gfs2_put_super,
 	.write_super		= gfs2_write_super,
+	.sync_fs		= gfs2_sync_fs,
 	.write_super_lockfs 	= gfs2_write_super_lockfs,
 	.unlockfs		= gfs2_unlockfs,
 	.statfs			= gfs2_statfs,