linux-kernel - Re: [PATCH v6 05/19] mm: memcontrol: decouple reference counting from page accounting

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Date:   Thu, 18 Jun 2020 07:55:35 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Roman Gushchin <guro@...com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Linux MM <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Kernel Team <kernel-team@...com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 05/19] mm: memcontrol: decouple reference counting from
 page accounting

Not sure if my email went through, so, re-sending.

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@...com> wrote:
>
> From: Johannes Weiner <hannes@...xchg.org>
>
[...]
> @@ -3003,13 +3004,16 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
>   */
>  void mem_cgroup_split_huge_fixup(struct page *head)
>  {
> +       struct mem_cgroup *memcg = head->mem_cgroup;
>         int i;
>
>         if (mem_cgroup_disabled())
>                 return;
>

A memcg NULL check is needed here.

> -       for (i = 1; i < HPAGE_PMD_NR; i++)
> -               head[i].mem_cgroup = head->mem_cgroup;
> +       for (i = 1; i < HPAGE_PMD_NR; i++) {
> +               css_get(&memcg->css);
> +               head[i].mem_cgroup = memcg;
> +       }
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>