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

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Date:	Tue, 11 Aug 2015 14:14:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Wanpeng Li <wanpeng.li@...mail.com>
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 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.


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