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From:   Yang Shi <shy828301@gmail.com>
Date:   Tue, 5 Oct 2021 19:35:35 -0700
Message-ID: <CAHbLzkpyxnvm3w0M_CEU7cYRCYr0coNCoiY1DvtnBzqb1R1nsw@mail.gmail.com>
Subject: Re: [v3 PATCH 1/5] mm: hwpoison: remove the unnecessary THP check
To:     =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= 
        <naoya.horiguchi@nec.com>, Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Peter Xu <peterx@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Linux MM <linux-mm@kvack.org>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi Naoya,

Any comment on this patch and patch #3? I'd prefer to fix more
comments for a new version.

Thanks,
Yang


On Thu, Sep 30, 2021 at 2:53 PM Yang Shi <shy828301@gmail.com> wrote:
>
> When handling THP hwpoison checked if the THP is in allocation or free
> stage since hwpoison may mistreat it as hugetlb page.  After
> commit 415c64c1453a ("mm/memory-failure: split thp earlier in memory error
> handling") the problem has been fixed, so this check is no longer
> needed.  Remove it.  The side effect of the removal is hwpoison may
> report unsplit THP instead of unknown error for shmem THP.  It seems not
> like a big deal.
>
> The following patch depends on this, which fixes shmem THP with
> hwpoisoned subpage(s) are mapped PMD wrongly.  So this patch needs to be
> backported to -stable as well.
>
> Cc: <stable@vger.kernel.org>
> Suggested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
>  mm/memory-failure.c | 14 --------------
>  1 file changed, 14 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 54879c339024..ed28eba50f98 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1147,20 +1147,6 @@ static int __get_hwpoison_page(struct page *page)
>         if (!HWPoisonHandlable(head))
>                 return -EBUSY;
>
> -       if (PageTransHuge(head)) {
> -               /*
> -                * Non anonymous thp exists only in allocation/free time. We
> -                * can't handle such a case correctly, so let's give it up.
> -                * This should be better than triggering BUG_ON when kernel
> -                * tries to touch the "partially handled" page.
> -                */
> -               if (!PageAnon(head)) {
> -                       pr_err("Memory failure: %#lx: non anonymous thp\n",
> -                               page_to_pfn(page));
> -                       return 0;
> -               }
> -       }
> -
>         if (get_page_unless_zero(head)) {
>                 if (head == compound_head(page))
>                         return 1;
> --
> 2.26.2
>