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From:   Yafang Shao <laoar.shao@gmail.com>
Date:   Thu, 18 Jun 2020 22:59:28 +0800
Message-ID: <CALOAHbCPd407z45e809VE5c8vP6ewqwkDkY9nrMP5TyP5cjG+A@mail.gmail.com>
Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page
To:     Chris Down <chris@chrisdown.name>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Michal Hocko <mhocko@kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        "Linux F2FS DEV, Mailing List" 
        <linux-f2fs-devel@lists.sourceforge.net>,
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        Andrew Morton <akpm@linux-foundation.org>,
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        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
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        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
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On Thu, Jun 18, 2020 at 8:37 PM Chris Down <chris@chrisdown.name> wrote:
>
> Yafang Shao writes:
> >On Thu, Jun 18, 2020 at 5:09 AM Chris Down <chris@chrisdown.name> wrote:
> >>
> >> Naresh Kamboju writes:
> >> >After this patch applied the reported issue got fixed.
> >>
> >> Great! Thank you Naresh and Michal for helping to get to the bottom of this :-)
> >>
> >> I'll send out a new version tomorrow with the fixes applied and both of you
> >> credited in the changelog for the detection and fix.
> >
> >As we have already found that the usage around memory.{emin, elow} has
> >many limitations, I think memory.{emin, elow} should be used for
> >memcg-tree internally only, that means they can only be used to
> >calculate the protection of a memcg in a specified memcg-tree but
> >should not be exposed to other MM parts.
>
> I agree that the current semantics are mentally taxing and we should generally
> avoid exposing the implementation details outside of memcg where possible. Do
> you have a suggested rework? :-)

Keeping the mem_cgroup_protected() as-is is my suggestion. Anyway I
think it is bad to put memory.{emin, elow} here and there.
If we don't have any better idea by now, just putting all the
references of memory.{emin, elow}  into one
wrapper(mem_cgroup_protected()) is the reasonable solution.

-- 
Thanks
Yafang