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Date:   Mon, 22 Aug 2022 16:16:03 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Yu Zhao <yuzhao@google.com>
Cc:     Suren Baghdasaryan <surenb@google.com>,
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Subject: Re: [PATCH RESEND v2 2/2] mm: delete unused MMF_OOM_VICTIM flag
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On Mon, 22 Aug 2022 16:59:29 -0600 Yu Zhao <yuzhao@google.com> wrote:

> > > @@ -4109,7 +4109,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned
> > > long start, unsigned long end,
> > >
> > >                 walk_pmd_range(&val, addr, next, args);
> > >
> > > -               if (mm_is_oom_victim(args->mm))
> > > +               if (test_bit(MMF_OOM_REAP_QUEUED, &args->mm->flags))
> > >                         return 1;
> > >
> > >                 /* a racy check to curtail the waiting time */
> >
> > Oh.  Why?  What does this change do?
> 
> The MMF_OOM_REAP_QUEUED flag is similar to the deleted MMF_OOM_VICTIM
> flag, but it's set at a later stage during an OOM kill.
> 
> When either is set, the OOM reaper is probably already freeing the
> memory of this mm_struct, or at least it's going to. So there is no
> need to dwell on it in the reclaim path, hence not about correctness.

Thanks.  That sounds worthy of some code comments?