make freeing super_block rcu-delayed

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/super.c

@@ -149,7 +149,7 @@ static void destroy_super(struct super_block *s)
 	WARN_ON(!list_empty(&s->s_mounts));
 	kfree(s->s_subtype);
 	kfree(s->s_options);
-	kfree(s);
+	kfree_rcu(s, rcu);
 }
 
 /**

include/linux/fs.h

@@ -1330,6 +1330,7 @@ struct super_block {
 	 */
 	struct list_lru		s_dentry_lru ____cacheline_aligned_in_smp;
 	struct list_lru		s_inode_lru ____cacheline_aligned_in_smp;
+	struct rcu_head		rcu;
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);