linux-ext4 - Re: mm: mkfs.ext4 invoked oom-killer on i386

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Message-ID: <20200528164121.GA839178@chrisdown.name>
Date:   Thu, 28 May 2020 17:41:21 +0100
From:   Chris Down <chris@...isdown.name>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Yafang Shao <laoar.shao@...il.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        "Linux F2FS DEV, Mailing List" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Arnd Bergmann <arnd@...db.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Theodore Ts'o <tytso@....edu>, Chao Yu <chao@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Chao Yu <yuchao0@...wei.com>, lkft-triage@...ts.linaro.org,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Cgroups <cgroups@...r.kernel.org>
Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page

Naresh Kamboju writes:
>On Thu, 28 May 2020 at 20:33, Michal Hocko <mhocko@...nel.org> wrote:
>>
>> On Fri 22-05-20 02:23:09, Naresh Kamboju wrote:
>> > My apology !
>> > As per the test results history this problem started happening from
>> > Bad : next-20200430 (still reproducible on next-20200519)
>> > Good : next-20200429
>> >
>> > The git tree / tag used for testing is from linux next-20200430 tag and reverted
>> > following three patches and oom-killer problem fixed.
>> >
>> > Revert "mm, memcg: avoid stale protection values when cgroup is above
>> > protection"
>> > Revert "mm, memcg: decouple e{low,min} state mutations from protectinn checks"
>> > Revert "mm-memcg-decouple-elowmin-state-mutations-from-protection-checks-fix"
>>
>> The discussion has fragmented and I got lost TBH.
>> In http://lkml.kernel.org/r/CA+G9fYuDWGZx50UpD+WcsDeHX9vi3hpksvBAWbMgRZadb0Pkww@mail.gmail.com
>> you have said that none of the added tracing output has triggered. Does
>> this still hold? Because I still have a hard time to understand how
>> those three patches could have the observed effects.
>
>On the other email thread [1] this issue is concluded.
>
>Yafang wrote on May 22 2020,
>
>Regarding the root cause, my guess is it makes a similar mistake that
>I tried to fix in the previous patch that the direct reclaimer read a
>stale protection value.  But I don't think it is worth to add another
>fix. The best way is to revert this commit.

This isn't a conclusion, just a guess (and one I think is unlikely). For this 
to reliably happen, it implies that the same race happens the same way each 
time.