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

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Message-Id: <20230411172617.13bc444955f51653b170f744@linux-foundation.org>
Date:   Tue, 11 Apr 2023 17:26:17 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Liu Shixin <liushixin2@...wei.com>
Cc:     Naoya Horiguchi <naoya.horiguchi@....com>,
        Tony Luck <tony.luck@...el.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] mm: hwpoison: support recovery from HugePage
 copy-on-write faults

On Tue, 11 Apr 2023 17:27:41 +0800 Liu Shixin <liushixin2@...wei.com> wrote:

> Patch a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults")
> introduced a new copy_user_highpage_mc() function, and fix the kernel crash
> when the kernel is copying a normal page as the result of a copy-on-write
> fault and runs into an uncorrectable error. But it doesn't work for HugeTLB.

What does "doesn't work" mean?  Please fully describe the user-visible
effects of the issue which this patch is addressing.

> This is to support HugeTLB by using copy_mc_user_highpage() in copy_subpage()
> and copy_user_gigantic_page() too.
> 
> Moreover, this is also used by userfaultfd, it will return -EHWPOISON if
> running into an uncorrectable error.