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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 26 Apr 2022 22:23:32 -0700
Message-ID: <CALvZod4oaj9MpBDVUp9KGmnqu4F3UxjXgOLkrkvmRfFjA7F1dw@mail.gmail.com>
Subject: Re: [PATCH memcg v4] net: set proper memcg for net_init hooks allocations
To:     Vasily Averin <vvs@openvz.org>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        Roman Gushchin <roman.gushchin@linux.dev>, kernel@openvz.org,
        Florian Westphal <fw@strlen.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        Cgroups <cgroups@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
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On Mon, Apr 25, 2022 at 11:43 PM Vasily Averin <vvs@openvz.org> wrote:
>
> __register_pernet_operations() executes init hook of registered
> pernet_operation structure in all existing net namespaces.
>
> Typically, these hooks are called by a process associated with
> the specified net namespace, and all __GFP_ACCOUNT marked
> allocation are accounted for corresponding container/memcg.
>
> However __register_pernet_operations() calls the hooks in the same
> context, and as a result all marked allocations are accounted
> to one memcg for all processed net namespaces.
>
> This patch adjusts active memcg for each net namespace and helps
> to account memory allocated inside ops_init() into the proper memcg.
>
> Signed-off-by: Vasily Averin <vvs@openvz.org>

Acked-by: Shakeel Butt <shakeelb@google.com>

[...]
>
> +static inline struct mem_cgroup *get_mem_cgroup_from_obj(void *p)
> +{
> +       struct mem_cgroup *memcg;
> +

Do we need memcg_kmem_enabled() check here or maybe
mem_cgroup_from_obj() should be doing memcg_kmem_enabled() instead of
mem_cgroup_disabled() as we can have "cgroup.memory=nokmem" boot
param.

> +       rcu_read_lock();
> +       do {
> +               memcg = mem_cgroup_from_obj(p);
> +       } while (memcg && !css_tryget(&memcg->css));
> +       rcu_read_unlock();
> +       return memcg;
> +}