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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Tue, 10 May 2022 09:35:09 -0700
Message-ID: <CAJuCfpHBURZCSq_bLpL5qsssUd1qEMK76K-5MwrdQvdW-pzaUg@mail.gmail.com>
Subject: Re: [PATCH 2/3] mm: drop oom code from exit_mmap
To:     Shuah Khan <skhan@linuxfoundation.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        David Rientjes <rientjes@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, Minchan Kim <minchan@kernel.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Christian Brauner <brauner@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Jann Horn <jannh@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Peter Xu <peterx@redhat.com>,
        John Hubbard <jhubbard@nvidia.com>, shuah@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, linux-kselftest@vger.kernel.org,
        kernel-team <kernel-team@android.com>
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On Tue, May 10, 2022 at 8:46 AM Shuah Khan <skhan@linuxfoundation.org> wrote:
>
> On 5/9/22 9:00 PM, Suren Baghdasaryan wrote:
> > With the oom-killer being able to operate on locked pages, exit_mmap
> > does not need to ensure that oom_reap_task_mm is done before it can
> > proceed. Instead it can rely on mmap_lock write lock to prevent
> > oom-killer from operating on the vma tree while it's freeing page
> > tables. exit_mmap can hold mmap_lock read lock when unmapping vmas
> > and then take mmap_lock write lock before freeing page tables.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >   include/linux/oom.h |  2 --
> >   mm/mmap.c           | 25 ++++++-------------------
> >   mm/oom_kill.c       |  2 +-
> >   3 files changed, 7 insertions(+), 22 deletions(-)
> >
>
> How does this improve the test? Include the information on why this
> change is needed as opposed describing what this does?

It doesn't improve the test. I used the test to verify this change and
wanted to keep them together so that others have an easy way to
exercise the same code path. That's the only relation between the test
and this cleanup. I'll split them into separate patchsets to avoid
further confusion.

>
> thanks,
> -- Shuah