linux-kernel - Re: [External] [PATCH 2/3] mm: Charge active memcg when no mm is set

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Date:   Mon, 29 Mar 2021 13:59:39 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     Dan Schatzberg <schatzberg.dan@...il.com>,
        Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Hugh Dickins <hughd@...gle.com>, Roman Gushchin <guro@...com>,
        Yang Shi <shy828301@...il.com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Yafang Shao <laoar.shao@...il.com>,
        Wei Yang <richard.weiyang@...il.com>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        Chris Down <chris@...isdown.name>
Subject: Re: [External] [PATCH 2/3] mm: Charge active memcg when no mm is set

On Mon, Mar 29, 2021 at 9:13 AM Muchun Song <songmuchun@...edance.com> wrote:
>
> On Mon, Mar 29, 2021 at 10:49 PM Dan Schatzberg
> <schatzberg.dan@...il.com> wrote:
[...]
>
> Since remote memcg must hold a reference, we do not
> need to do something like get_active_memcg() does.
> Just use css_get to obtain a ref, it is simpler. Just
> Like below.
>
> +       if (unlikely(!mm)) {
> +               memcg = active_memcg();
> +               if (unlikely(memcg)) {
> +                       /* remote memcg must hold a ref. */
> +                       css_get(memcg);
> +                       return memcg;
> +               }
>

I second Muchun's suggestion.