linux-kernel - Re: [REGRESSION] Re: [PATCH 6.1 033/219] memcg: drop kmem.limit_in

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Date:   Wed, 20 Sep 2023 22:08:11 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Muchun Song <muchun.song@...ux.dev>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, patches@...ts.linux.dev,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, regressions@...ts.linux.dev,
        mathieu.tortuyaux@...il.com
Subject: Re: [REGRESSION] Re: [PATCH 6.1 033/219] memcg: drop
 kmem.limit_in_bytes

On Wed 20-09-23 12:46:23, Shakeel Butt wrote:
> On Wed, Sep 20, 2023 at 9:55 AM Michal Hocko <mhocko@...e.com> wrote:
> >
> > On Wed 20-09-23 08:32:42, Shakeel Butt wrote:
> > > Also I don't think reverting 58056f77502f would give any benefit.
> >
> > Not reverting 58056f77502f would re-introduce the regression in some
> > non-patched versions of Docker runtimes which cannot handle ENOTSUPP.
> > So I think we need to revert both or none of them. I would prefer the
> > later (option 1) as the fix is trivial but I do understand headache
> > of chasing all those outdated deployments or vendor code forks.
> 
> I think that would be too much conservative an approach but I don't

Well, TBH I do not really see any sifference between one set of broken
userspace or the other. Both are making assumptions on our interfaces
and they do not overlap unfortunately.

> have a strong opinion against it. Also just to be clear we are not
> talking about full revert of 58056f77502f but just the returning of
> EOPNOTSUPP, right?

If we allow the limit to be set without returning a failure then we
still have options 2 and 3 on how to deal with that. One of them is to
enforce the limit.

-- 
Michal Hocko
SUSE Labs