Re: [PATCH 1/2] mm, memcg: Avoid stale protection values when cgroup is above protection

[Michal Hocko]

On Fri 01-05-20 07:59:57, Yafang Shao wrote:
> On Thu, Apr 30, 2020 at 10:57 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> >
> > On Wed 29-04-20 12:56:27, Johannes Weiner wrote:
> > [...]
> > > I think to address this, we need a more comprehensive solution and
> > > introduce some form of serialization. I'm not sure yet how that would
> > > look like yet.
> >
> > Yeah, that is what I've tried to express earlier and that is why I would
> > rather go with an uglier workaround for now and think about a more
> > robust effective values calculation on top.
> >
> 
> Agreed.
> If there's a more robust effective values calculation on top, then we
> don't need to hack it here and there.
> 
> > > I'm still not sure it's worth having a somewhat ugly workaround in
> > > mem_cgroup_protection() to protect against half of the bug. If you
> > > think so, the full problem should at least be documented and marked
> > > XXX or something.
> >
> > Yes, this makes sense to me. What about the following?
> 
> Many thanks for the explaination on this workaround.
> With this explanation, I think the others will have a clear idea why
> we must add this ugly workaround here.

OK, this would be the patch with the full changelog. If both Chris and
Johannes are ok with this I would suggest replacing the one Andrew took
already