linux-kernel - Re: [PATCH V2] mm: fix kernel crash in khugepaged thread

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Date:	Thu, 12 Nov 2015 15:15:01 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	jmarchan@...hat.com, mgorman@...hsingularity.net,
	Ebru Akagunduz <ebru.akagunduz@...il.com>,
	willy@...ux.intel.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mm: fix kernel crash in khugepaged thread

Ok
i will send a V3 patch.
> On Nov 5, 2015, at 16:50, Kirill A. Shutemov <kirill@...temov.name> wrote:
> 
> On Thu, Nov 05, 2015 at 09:12:34AM +0100, Vlastimil Babka wrote:
>> On 10/29/2015 01:35 AM, Kirill A. Shutemov wrote:
>>>> @@ -2605,9 +2603,9 @@ out_unmap:
>>>> 		/* collapse_huge_page will return with the mmap_sem released */
>>>> 		collapse_huge_page(mm, address, hpage, vma, node);
>>>> 	}
>>>> -out:
>>>> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
>>>> -				     none_or_zero, result, unmapped);
>>>> +	trace_mm_khugepaged_scan_pmd(mm, pte_present(pteval) ?
>>>> +			pte_pfn(pteval) : -1, writable, referenced,
>>>> +			none_or_zero, result, unmapped);
>>> 
>>> maybe passing down pte instead of pfn?
>> 
>> Maybe just pass the page, and have tracepoint's fast assign check for !NULL and
>> do page_to_pfn itself? That way the complexity and overhead is only in the
>> tracepoint and when enabled.
> 
> Agreed.
> 
> -- 
> Kirill A. Shutemov

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