linux-kernel - Re: [External] Re: [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one

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Message-ID: <CAMZfGtW52Du6XXVSGcziFG8HSK5G=Xu12p7-F+TOjWM0hizUkQ@mail.gmail.com>
Date:   Wed, 13 Jan 2021 19:03:21 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andi Kleen <ak@...ux.intel.com>, mhocko@...e.cz,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Yang Shi <shy828301@...il.com>, Michal Hocko <mhocko@...e.com>
Subject: Re: [External] Re: [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB
 page whose refcount is one

On Wed, Jan 13, 2021 at 6:57 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Wed, Jan 13, 2021 at 01:22:04PM +0800, Muchun Song wrote:
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 4385f2fb5d18..a6631c4eb6a6 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> >               return -ENOSYS;
> >       }
> >
> > +     if (page_count(hpage) == 1) {
> > +             /* page was freed from under us. So we are done. */
> > +             putback_active_hugepage(hpage);
> > +             return MIGRATEPAGE_SUCCESS;
> > +     }
> > +
>
> I was a bit puzzled as why we did not go to the "goto" block that already does
> this, but then I saw the put_new_page/new_hpage handlind further down.
> It could be re-arranged but out of scope, so:

Agree. I also thought about this. :)

>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
>

Thanks.

>
> --
> Oscar Salvador
> SUSE L3