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

Michal Hocko
2017-11-23T14:06:03Z

On Thu 23-11-17 22:57:06, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > @@ -260,9 +261,8 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
> > > s->s_shrink.count_objects = super_cache_count;
> > > s->s_shrink.batch = 1024;
> > > s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
> > > - INIT_LIST_HEAD(&s->s_shrink.list);
> > > - return s;
> > > -
> > > + if (register_shrinker(&s->s_shrink) == 0)
> > > + return s;
> > > fail:
> > > destroy_unused_super(s);
> > > return NULL;
> >
> > But I am not sure this is correct. So what protects shrinker invocation
> > while the object is not initialized yet?
>
> Then, what protects shrinker invocation in your patch?

It is s_umount lock but that one is alreay held at the point where you
suggested register_shrinker. My bad, I could have noticed that. Feel
free to take over and send a patch. Considering I've screwed several
times already I do not feel I am the right one to send the fix.

--
Michal Hocko
SUSE Labs