Re: [f2fs-dev] mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page

From: Chris Down <chris@chrisdown.name>
To: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: lkft-triage@lists.linaro.org, Michal Hocko <mhocko@kernel.org>,
	linux-mm <linux-mm@kvack.org>, Yafang Shao <laoar.shao@gmail.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Cgroups <cgroups@vger.kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Anders Roxell <anders.roxell@linaro.org>,
	Hugh Dickins <hughd@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Linux-Next Mailing List <linux-next@vger.kernel.org>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-block <linux-block@vger.kernel.org>,
	Jaegeuk Kim <jaegeuk@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
	open list <linux-kernel@vger.kernel.org>,
	"Linux F2FS DEV,
	Mailing List" <linux-f2fs-devel@lists.sourceforge.net>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>
Subject: Re: [f2fs-dev] mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page
Date: Thu, 28 May 2020 17:41:21 +0100	[thread overview]
Message-ID: <20200528164121.GA839178@chrisdown.name> (raw)
In-Reply-To: <CA+G9fYvDXiZ9E9EfU6h0gsJ+xaXY77mRu9Jg+J7C=X4gJ3qvLg@mail.gmail.com>

Naresh Kamboju writes:
>On Thu, 28 May 2020 at 20:33, Michal Hocko <mhocko@kernel.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.

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