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From:   Barry Song <21cnbao@gmail.com>
Date:   Wed, 8 Jun 2022 19:48:17 +1200
Message-ID: <CAGsJ_4w6JjuG4rn2P=d974wBOUtXUUnaZKnx+-G6a8_mSROa+Q@mail.gmail.com>
Subject: Re: [PATCH v11 07/14] mm: multi-gen LRU: exploit locality in rmap
To:     Yu Zhao <yuzhao@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>, Andi Kleen <ak@linux.intel.com>,
        Aneesh Kumar <aneesh.kumar@linux.ibm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
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        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Michael Larabel <Michael@michaellarabel.com>,
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        Tejun Heo <tj@kernel.org>, Vlastimil Babka <vbabka@suse.cz>,
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        Shuang Zhai <szhai2@cs.rochester.edu>,
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        Vaibhav Jain <vaibhav@linux.ibm.com>, huzhanyuan@oppo.com
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On Wed, Jun 8, 2022 at 7:07 AM Yu Zhao <yuzhao@google.com> wrote:
>
> On Tue, Jun 7, 2022 at 1:37 AM Barry Song <21cnbao@gmail.com> wrote:
> >
> > On Mon, Jun 6, 2022 at 9:25 PM Barry Song <21cnbao@gmail.com> wrote:
> > >
> > > On Wed, May 18, 2022 at 4:49 PM Yu Zhao <yuzhao@google.com> wrote:
>
> ...
>
> > I can't really explain why we are getting a random app/java vm crash in monkey
> > test by using ptep_test_and_clear_young() only in lru_gen_look_around() on an
> > armv8-a machine without hardware PTE young support.
> >
> > Moving to  ptep_clear_flush_young() in look_around can make the random
> > hang disappear according to zhanyuan(Cc-ed).
>
> This sounds too familiar -- let me ask again: was the following commit
> included during the test?
>
>   07509e10dcc7 arm64: pgtable: Fix pte_accessible()
>
> If not, it will cause exactly the problem you described. And what
> about this one?
>
>   e914d8f00391 mm: fix unexpected zeroed page mapping with zram swap
>
> Missing it also causes userspace memory corruption on Android, i.e.,
> random app crashes.
>

According to zhanyuan's testing, we can confirm the above two commits
can fix the random android crash.

Thanks
Barry