linux-kernel - Re: [PATCH v2] mm: check_new_page_bad() directly returns in __PG

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Message-ID: <573F1EC0.6030801@suse.cz>
Date:	Fri, 20 May 2016 16:27:12 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v2] mm: check_new_page_bad() directly returns in
 __PG_HWPOISON case

On 05/18/2016 04:03 PM, Mel Gorman wrote:
> On Wed, May 18, 2016 at 10:09:50AM +0000, Naoya Horiguchi wrote:
>>  From c600b1ee6c36b3df6973f5365b4179c92f3c08e3 Mon Sep 17 00:00:00 2001
>> From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>> Date: Wed, 18 May 2016 18:42:57 +0900
>> Subject: [PATCH v2] mm: check_new_page_bad() directly returns in __PG_HWPOISON
>>   case
>>
>> Currently we check page->flags twice for "HWPoisoned" case of
>> check_new_page_bad(), which can cause a race with unpoisoning.
>> This race unnecessarily taints kernel with "BUG: Bad page state".
>> check_new_page_bad() is the only caller of bad_page() which is interested
>> in __PG_HWPOISON, so let's move the hwpoison related code in bad_page()
>> to it.
>>
>> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>
> Acked-by: Mel Gorman <mgorman@...hsingularity.net>
>
Acked-by: Vlastimil Babka <vbabka@...e.cz>