remove the call to ->write_super in __sync_filesystem

Now that all filesystems provide ->sync_fs methods we can change
__sync_filesystem to only call ->sync_fs.

This gives us a clear separation between periodic writeouts which
are driven by ->write_super and data integrity syncs that go
through ->sync_fs. (modulo file_fsync which is also going away)
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/sync.c

@@ -33,8 +33,6 @@ static int __sync_filesystem(struct super_block *sb, int wait)
 	else
 		sync_quota_sb(sb, -1);
 	sync_inodes_sb(sb, wait);
-	if (sb->s_dirt && sb->s_op->write_super)
-		sb->s_op->write_super(sb);
 	if (sb->s_op->sync_fs)
 		sb->s_op->sync_fs(sb, wait);
 	return __sync_blockdev(sb->s_bdev, wait);