linux-kernel - Re: [PATCH 1/3] mm, memcg: add mem_cgroup_disabled checks in vmpressure and swap-related functions

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Message-ID: <CALvZod7MUemu_=ffcE3tpg_=Mazcp6OB=fSJxC9Sa2-uPPLqbA@mail.gmail.com>
Date:   Fri, 9 Jul 2021 09:00:39 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Muchun Song <songmuchun@...edance.com>,
        Yang Shi <shy828301@...il.com>, alexs@...nel.org,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Minchan Kim <minchan@...nel.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH 1/3] mm, memcg: add mem_cgroup_disabled checks in
 vmpressure and swap-related functions

On Thu, Jul 8, 2021 at 5:05 PM Suren Baghdasaryan <surenb@...gle.com> wrote:
>
[...]

> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -240,7 +240,12 @@ static void vmpressure_work_fn(struct work_struct *work)
>  void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
>                 unsigned long scanned, unsigned long reclaimed)
>  {
> -       struct vmpressure *vmpr = memcg_to_vmpressure(memcg);
> +       struct vmpressure *vmpr;
> +
> +       if (mem_cgroup_disabled())
> +               return;
> +
> +       vmpr = memcg_to_vmpressure(memcg);

I was wondering why this was not crashing but realized that we
allocate root_mem_cgroup even in cgroup_disable=memory case.

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>