linux-kernel - Re: [PATCH v2] cgroup: memcg: net: do not associate sock with unrelated cgroup

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Date:   Fri, 14 Feb 2020 16:04:20 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>,
        Greg Thelen <gthelen@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Cgroups <cgroups@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        Roman Gushchin <guro@...com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] cgroup: memcg: net: do not associate sock with
 unrelated cgroup

On Fri, Feb 14, 2020 at 3:12 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Fri, Feb 14, 2020 at 2:48 PM Shakeel Butt <shakeelb@...gle.com> wrote:
>
> >
> > I think in the current code if the association is skipped at
> > allocation time then the sock will remain unassociated for its
> > lifetime.
> >
> > Maybe we can add the association in the later stages but it seems like
> > it is not a simple task i.e. edbe69ef2c90f ("Revert "defer call to
> > mem_cgroup_sk_alloc()"").
>
> Half TCP sockets are passive, so this means that 50% of TCP sockets
> won't be charged.
> (the socket cloning always happens from BH context)
>
> I think this deserves a comment in the changelog or documentation,
> otherwise some people might think
> using memcg will make them safe.

Thanks I will update the changelog. Also is inet_csk_accept() the
right place for delayed cgroup/memcg binding (if we decide to do
that). I am wondering if we can force charge the memcg during late
binding to cater the issue fixed in edbe69ef2c90f.

Shakeel