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Subject: Re: [mm 4.15-rc8] Random oopses under memory pressure.
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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From: Dave Hansen <dave.hansen@linux.intel.com>
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Date: Thu, 18 Jan 2018 06:38:10 -0800
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On 01/18/2018 05:12 AM, Kirill A. Shutemov wrote:
> -		if (pte_page(*pvmw->pte) - pvmw->page >=
> -				hpage_nr_pages(pvmw->page)) {

Is ->pte guaranteed to map a page which is within the same section as
pvmw->page?  Otherwise, with sparsemem (non-vmemmap), the pointer
arithmetic won't work.

WARN_ON_ONCE(page_to_section(pvmw->page) !=
	     page_to_section(pte_page(*pvmw->pte));

Will detect that.