Preparation to adding new method:
 new helper - shutdown_super().  It is cut from kill_super() and
 it had absorbed all actions done with superblock contents -
 now kill_super(s) is simply

	struct file_system_type *fs = s->s_type;
	if (!deactivate_super(s))
		return;
		shutdown_super(s);
	put_filesystem(fs);

 and shutdown_super() is going to become a method.