linux-kernel - Re: [PATCH 15/16] mm/migration: fix possible do_pages_stat

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Message-ID: <CAMZfGtXKa73ZVLtJeE5O40rOgn7oZkxP5CB+q5t--ihUerfKew@mail.gmail.com>
Date:   Mon, 7 Mar 2022 15:01:12 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Yang Shi <shy828301@...il.com>,
        Matthew Wilcox <willy@...radead.org>, Zi Yan <ziy@...dia.com>,
        Minchan Kim <minchan@...nel.org>,
        Alistair Popple <apopple@...dia.com>,
        ave.hansen@...ux.intel.com, o451686892@...il.com,
        Mina Almasry <almasrymina@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Peter Xu <peterx@...hat.com>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>, Michal Hocko <mhocko@...e.com>,
        riel@...hat.com, Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 15/16] mm/migration: fix possible do_pages_stat_array
 racing with memory offline

On Mon, Mar 7, 2022 at 1:22 PM Huang, Ying <ying.huang@...el.com> wrote:
>
> Miaohe Lin <linmiaohe@...wei.com> writes:
>
> > When follow_page peeks a page, the page could be reclaimed under heavy
> > memory pressure
>
> I don't think that memory pressure and reclaiming will be an issue.

I think he means a page first to be reclaimed then to be offline
could encounter this issue and reclaiming is a precondition.

Thanks.

>
> > and thus be offlined while it's still being used by the
> > do_pages_stat_array().
>
> "offline" seems a possible problem.