linux-kernel - [PATCH v2 0/2] mm, oom: do not grant oom victims full memory reserves access

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Date:   Thu, 10 Aug 2017 09:50:17 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mel Gorman <mgorman@...e.de>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        David Rientjes <rientjes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 0/2] mm, oom: do not grant oom victims full memory reserves access

Hi,
this is a second version of the series previously posted [1]. Tetsuo
has noticed a bug I've introduced during the rebase and also pointed
out reserves access changes on nommu arches which I have addressed
as well. Mel had some more feedback which is hopefully addressed as
well. There were no further comments so I am reposting and asking for
inclusion.

this is a part of a larger series I posted back in Oct last year [2]. I
have dropped patch 3 because it was incorrect and patch 4 is not
applicable without it.

The primary reason to apply patch 1 is to remove a risk of the complete
memory depletion by oom victims. While this is a theoretical risk right
now there is a demand for memcg aware oom killer which might kill all
processes inside a memcg which can be a lot of tasks. That would make
the risk quite real.

This issue is addressed by limiting access to memory reserves. We no
longer use TIF_MEMDIE to grant the access and use tsk_is_oom_victim
instead. See Patch 1 for more details. Patch 2 is a trivial follow up
cleanup.

I would still like to get rid of TIF_MEMDIE completely but I do not have
time to do it now and it is not a pressing issue.

[1] http://lkml.kernel.org/r/20170727090357.3205-1-mhocko@kernel.org
[2] http://lkml.kernel.org/r/20161004090009.7974-1-mhocko@kernel.org