linux-kernel - Re: [PATCH] mm: workingset: fix NULL ptr in count_shadow

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Message-ID: <CAKTCnzmZ1cwmtg+p3=3rTQJbf12VmFzWJcM+wsAdNN20v1DMDw@mail.gmail.com>
Date:   Fri, 2 Dec 2016 08:24:16 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Marek Marczykowski-Górecki 
        <marmarek@...uw.edu.pl>, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: workingset: fix NULL ptr in count_shadow_nodes

On Fri, Dec 2, 2016 at 12:21 AM, Michal Hocko <mhocko@...nel.org> wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> 0a6b76dd23fa ("mm: workingset: make shadow node shrinker memcg aware")
> has made the workingset shadow nodes shrinker memcg aware. The
> implementation is not correct though because memcg_kmem_enabled() might
> become true while we are doing a global reclaim when the sc->memcg might
> be NULL which is exactly what Marek has seen:
>
<snip>
>
> -       if (memcg_kmem_enabled()) {
> +       if (sc->memcg) {
>                 pages = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
>                                                      LRU_ALL_FILE);
>         } else {

Acked-by: Balbir Singh <bsingharora@...il.com>