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Date:   Mon, 22 Aug 2022 15:48:22 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Yu Zhao <yuzhao@google.com>
Cc:     Suren Baghdasaryan <surenb@google.com>,
        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>,
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        hch@infradead.org, oleg@redhat.com,
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        Jann Horn <jannh@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Peter Xu <peterx@redhat.com>,
        John Hubbard <jhubbard@nvidia.com>, shuah@kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, linux-kselftest@vger.kernel.org,
        kernel-team@android.com
Subject: Re: [PATCH RESEND v2 2/2] mm: delete unused MMF_OOM_VICTIM flag
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On Mon, 22 Aug 2022 16:33:51 -0600 Yu Zhao <yuzhao@google.com> wrote:

> > --- a/mm/vmscan.c~mm-delete-unused-mmf_oom_victim-flag-fix
> > +++ a/mm/vmscan.c
> > @@ -3429,9 +3429,6 @@ static bool should_skip_mm(struct mm_str
> >         if (size < MIN_LRU_BATCH)
> >                 return true;
> >
> > -       if (mm_is_oom_victim(mm))
> > -               return true;
> > -
> >         return !mmget_not_zero(mm);
> >  }
> >
> > @@ -4127,9 +4124,6 @@ restart:
> >
> >                 walk_pmd_range(&val, addr, next, args);
> >
> > -               if (mm_is_oom_victim(args->mm))
> > -                       return 1;
> > -
> >                 /* a racy check to curtail the waiting time */
> >                 if (wq_has_sleeper(&walk->lruvec->mm_state.wait))
> >                         return 1;
> > _
> >
> > Please confirm?
> 
> LGTM.  The deleted checks are not about correctness.

OK, for now.

> I've queued
> 
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3402,7 +3402,7 @@ static bool should_skip_mm(struct mm_struct *mm,
> struct lru_gen_mm_walk *walk)
>         if (size < MIN_LRU_BATCH)
>                 return true;
> 
> -       if (mm_is_oom_victim(mm))
> +       if (test_bit(MMF_OOM_REAP_QUEUED, &mm->flags))
>                 return true;
> 
>         return !mmget_not_zero(mm);
> @@ -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?