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From: Balbir Singh <bsingharora@gmail.com>
Date: Fri, 2 Dec 2016 08:24:16 +1100
Message-ID: <CAKTCnzmZ1cwmtg+p3=3rTQJbf12VmFzWJcM+wsAdNN20v1DMDw@mail.gmail.com>
Subject: Re: [PATCH] mm: workingset: fix NULL ptr in count_shadow_nodes
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        =?UTF-8?Q?Marek_Marczykowski=2DG=C3=B3recki?= 
        <marmarek@mimuw.edu.pl>,
        linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
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On Fri, Dec 2, 2016 at 12:21 AM, Michal Hocko <mhocko@kernel.org> wrote:
> From: Michal Hocko <mhocko@suse.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@gmail.com>

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In-Reply-To: <20161201132156.21450-1-mhocko@kernel.org>
References: <20161201132156.21450-1-mhocko@kernel.org>
From: Balbir Singh <bsingharora@gmail.com>
Date: Fri, 2 Dec 2016 08:24:16 +1100
Message-ID: <CAKTCnzmZ1cwmtg+p3=3rTQJbf12VmFzWJcM+wsAdNN20v1DMDw@mail.gmail.com>
Subject: Re: [PATCH] mm: workingset: fix NULL ptr in count_shadow_nodes
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Sender: owner-linux-mm@kvack.org
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To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <hannes@cmpxchg.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, =?UTF-8?Q?Marek_Marczykowski=2DG=C3=B3recki?= <marmarek@mimuw.edu.pl>, linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>

On Fri, Dec 2, 2016 at 12:21 AM, Michal Hocko <mhocko@kernel.org> wrote:
> From: Michal Hocko <mhocko@suse.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@gmail.com>

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