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In-Reply-To: <20210817053703.2267588-1-naoya.horiguchi@linux.dev>
From:   Yang Shi <shy828301@gmail.com>
Date:   Wed, 18 Aug 2021 11:07:43 -0700
Message-ID: <CAHbLzkrHOHNRQU-TtR6cV9stV-c88jxg+LWbJBbBifh1n74FKw@mail.gmail.com>
Subject: Re: [PATCH v1] mm/hwpoison: Retry with shake_page() for unhandlable pages
To:     Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc:     Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tony Luck <tony.luck@intel.com>,
        Oscar Salvador <osalvador@suse.de>,
        Muchun Song <songmuchun@bytedance.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Michal Hocko <mhocko@suse.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, Aug 16, 2021 at 10:37 PM Naoya Horiguchi
<naoya.horiguchi@linux.dev> wrote:
>
> From: Naoya Horiguchi <naoya.horiguchi@nec.com>
>
> HWPoisonHandlable() sometimes returns false for typical user pages
> due to races with average memory events like transfers over LRU lists.
> This causes failures in hwpoison handling.
>
> There's retry code for such a case but does not work because the retry
> loop reaches the retry limit too quickly before the page settles down to
> handlable state. Let get_any_page() call shake_page() to fix it.
>
> Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation")
> Reported-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> Cc: stable@vger.kernel.org # 5.13
> ---
>  mm/memory-failure.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git v5.14-rc6/mm/memory-failure.c v5.14-rc6_patched/mm/memory-failure.c
> index eefd823deb67..aa6592540f17 100644
> --- v5.14-rc6/mm/memory-failure.c
> +++ v5.14-rc6_patched/mm/memory-failure.c
> @@ -1146,7 +1146,7 @@ static int __get_hwpoison_page(struct page *page)
>          * unexpected races caused by taking a page refcount.
>          */
>         if (!HWPoisonHandlable(head))
> -               return 0;
> +               return -EBUSY;
>
>         if (PageTransHuge(head)) {
>                 /*
> @@ -1199,9 +1199,14 @@ static int get_any_page(struct page *p, unsigned long flags)
>                         }
>                         goto out;
>                 } else if (ret == -EBUSY) {
> -                       /* We raced with freeing huge page to buddy, retry. */
> -                       if (pass++ < 3)
> +                       /*
> +                        * We raced with (possibly temporary) unhandlable
> +                        * page, retry.
> +                        */
> +                       if (pass++ < 3) {
> +                               shake_page(p, 1);
>                                 goto try_again;
> +                       }

I think the return value should be set to -EIO before jumping to out.
I'm supposed -EIO means this is really or very likely an unhandlable
page.

>                         goto out;
>                 }
>         }
> --
> 2.25.1
>
>