linux-kernel - Re: [PATCH] mm/hwpoison: fix panic due to split huge zero page

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Date:	Wed, 12 Aug 2015 06:20:33 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [PATCH] mm/hwpoison: fix panic due to split huge zero page



On 8/12/15 5:14 AM, Andrew Morton wrote:
> On Tue, 11 Aug 2015 18:47:57 +0800 Wanpeng Li <wanpeng.li@...mail.com> wrote:
>
>> ...
>>
>> Huge zero page is allocated if page fault w/o FAULT_FLAG_WRITE flag.
>> The get_user_pages_fast() which called in madvise_hwpoison() will get
>> huge zero page if the page is not allocated before. Huge zero page is
>> a tranparent huge page, however, it is not an anonymous page. memory_failure
>> will split the huge zero page and trigger BUG_ON(is_huge_zero_page(page));
>> After commit (98ed2b0: mm/memory-failure: give up error handling for
>> non-tail-refcounted thp), memory_failure will not catch non anon thp
>> from madvise_hwpoison path and this bug occur.
> So I'm assuming this patch is needed for 4.2 but not in earlier
> kernels.

I think so. :-)  Btw, how about my other hwpoison patches?

Regards,
Wanpeng Li

>

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