linux-kernel - Re: [PATCH -next v2] mm: hwpoison: support recovery from HugePage copy-on-write faults

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Date:   Fri, 14 Apr 2023 02:57:03 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Liu Shixin <liushixin2@...wei.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Tony Luck <tony.luck@...el.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Muchun Song <muchun.song@...ux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next v2] mm: hwpoison: support recovery from HugePage
 copy-on-write faults

On Thu, Apr 13, 2023 at 09:13:49PM +0800, Liu Shixin wrote:
> copy-on-write of hugetlb user pages with uncorrectable errors will result
> in a kernel crash. This is because the copy is performed in kernel mode
> and in general we can not handle accessing memory with such errors while
> in kernel mode. Commit a873dfe1032a ("mm, hwpoison: try to recover from
> copy-on write faults") introduced the routine copy_user_highpage_mc() to
> gracefully handle copying of user pages with uncorrectable errors. However,
> the separate hugetlb copy-on-write code paths were not modified as part
> of commit a873dfe1032a.
> 
> Modify hugetlb copy-on-write code paths to use copy_mc_user_highpage()
> so that they can also gracefully handle uncorrectable errors in user
> pages. This involves changing the hugetlb specific routine
> copy_user_large_folio() from type void to int so that it can return an error.
> Modify the hugetlb userfaultfd code in the same way so that it can return
> -EHWPOISON if it encounters an uncorrectable error.
> 
> Signed-off-by: Liu Shixin <liushixin2@...wei.com>
> Acked-by: Mike Kravetz <mike.kravetz@...cle.com>

Looks good to me.

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@....com>