Re: [PATCH v2] fs: handle shrinker registration failure in sget_userns

[Al Viro]

On Thu, Nov 23, 2017 at 03:35:37PM +0100, Michal Hocko wrote:
> Hopefully less screwed version.  But as I've said I am not really
> familiar with the code and do not feel competent to change it so please
> be very careful here. I've moved the shrinker registration to
> alloc_super which turned out to be simpler.

I don't get it.  Why the hell do we need all that PITA in the first place?
Just make sget_userns() end with
        if (unlikely(regsiter_shrinker(&s->s_shrink) != 0)) {
                deactivate_locked_super(s);
                s = ERR_PTR(-ENOMEM);
        }
        return s;
and be done with that.  All there is to it...