linux-kernel - Re: [PATCH] mm, page_alloc: prevent infinite loop in buffered

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Message-ID: <20160530105745.GO2527@techsingularity.net>
Date:	Mon, 30 May 2016 11:57:45 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm, page_alloc: prevent infinite loop in
 buffered_rmqueue()

On Mon, May 30, 2016 at 11:46:05AM +0200, Vlastimil Babka wrote:
> On 05/30/2016 11:01 AM, Mel Gorman wrote:
> >From: Vlastimil Babka <vbabka@...e.cz>
> >
> >In DEBUG_VM kernel, we can hit infinite loop for order == 0 in
> >buffered_rmqueue() when check_new_pcp() returns 1, because the bad page is
> >never removed from the pcp list. Fix this by removing the page before retrying.
> >Also we don't need to check if page is non-NULL, because we simply grab it from
> >the list which was just tested for being non-empty.
> >
> >Fixes: http://www.ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-defer-debugging-checks-of-freed-pages-until-a-pcp-drain.patch
> 
> That was a wrong one, which I corrected later. Also it's no longer mmotm.
> Correction below:
> 
> Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages
> allocated from the PCP")
> 

Yes sorry, I meant to clean it up but had just re-read the patch itself,
confirmed it was missing and was still required.

-- 
Mel Gorman
SUSE Labs