Re: [PATCH] fs: handle shrinker registration failure in sget_userns

[Al Viro]

On Thu, Nov 23, 2017 at 12:52:47PM +0100, Michal Hocko wrote:
> @@ -503,12 +504,18 @@ struct super_block *sget_userns(struct file_system_type 
> *type,
>               s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
>               if (!s)
>                       return ERR_PTR(-ENOMEM);
> +             if (register_shrinker(&s->s_shrink)) {
> +                     spin_unlock(&sb_lock);
> +                     destroy_unused_super(s);
> +                     return ERR_PTR(-ENOMEM);

Have you even tested that?  What the hell is that spin_unlock() doing there?