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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 16 Nov 2021 13:55:54 -0800
Message-ID: <CALvZod7FHO6edK1cR+rbt6cG=+zUzEx3+rKWT5mi73Q29_Y5qA@mail.gmail.com>
Subject: Re: [PATCH v3 2/4] mm/oom: handle remote ooms
To:     Mina Almasry <almasrymina@google.com>
Cc:     Michal Hocko <mhocko@suse.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Roman Gushchin <guro@fb.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tejun Heo <tj@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Muchun Song <songmuchun@bytedance.com>, riel@surriel.com,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        cgroups@vger.kernel.org
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On Tue, Nov 16, 2021 at 1:27 PM Mina Almasry <almasrymina@google.com> wrote:
>
> On Tue, Nov 16, 2021 at 3:29 AM Michal Hocko <mhocko@suse.com> wrote:
[...]
> > Yes, exactly. I meant that all this special casing would be done at the
> > shmem layer as it knows how to communicate this usecase.
> >
>
> Awesome. The more I think of it I think the ENOSPC handling is perfect
> for this use case, because it gives all users of the shared memory and
> remote chargers a chance to gracefully handle the ENOSPC or the SIGBUS
> when we hit the nothing to kill case. The only issue is finding a
> clean implementation, and if the implementation I just proposed sounds
> good to you then I see no issues and I'm happy to submit this in the
> next version. Shakeel and others I would love to know what you think
> either now or when I post the next version.
>

The direction seems reasonable to me. I would have more comments on
the actual code. At the high level I would prefer not to expose these
cases in the filesystem code (shmem or others) and instead be done in
a new memcg interface for filesystem users.