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

From: Andrew Morton
Date: Tue Aug 11 2015 - 17:14:12 EST


On Tue, 11 Aug 2015 18:47:57 +0800 Wanpeng Li <wanpeng.li@xxxxxxxxxxx> 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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