linux-kernel - Re: [PATCH v1 1/5] mm, hwpoison, hugetlb: introduce SUBPAGE_INDEX

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Message-ID: <ea4cc6c8-a772-dce0-a7a3-4c3ceb31735f@redhat.com>
Date:   Tue, 7 Jun 2022 15:04:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/5] mm, hwpoison, hugetlb: introduce
 SUBPAGE_INDEX_HWPOISON to save raw error page

On 02.06.22 07:06, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> When handling memory error on a hugetlb page, the error handler tries to
> dissolve and turn it into 4kB pages.  If it's successfully dissolved,
> PageHWPoison flag is moved to the raw error page, so that's all right.
> However, dissolve sometimes fails, then the error page is left as
> hwpoisoned hugepage. It's useful if we can retry to dissolve it to save
> healthy pages, but that's not possible now because the information about
> where the raw error page is lost.
> 
> Use the private field of a tail page to keep that information.  The code
> path of shrinking hugepage pool used this info to try delayed dissolve.
> This only keeps one hwpoison page for now, which might be OK because it's
> simple and multiple hwpoison pages in a hugepage can be rare. But it can
> be extended in the future.
> 
>

But what would happen now if you have multiple successive MCE events on
such a page now?

-- 
Thanks,

David / dhildenb