linux-kernel - Re: [PATCH v4 1/4] mm/page_alloc: fix incorrect isolation behavior by rechecking migratetype

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Date:	Tue, 28 Oct 2014 16:22:31 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Heesub Shin <heesub.shin@...sung.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	t.stanislaws@...sung.com, Gioh Kim <gioh.kim@....com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v4 1/4] mm/page_alloc: fix incorrect isolation behavior
 by rechecking migratetype

On Mon, Oct 27, 2014 at 11:33:20AM +0100, Vlastimil Babka wrote:
> On 10/23/2014 10:10 AM, Joonsoo Kim wrote:
> > Changes from v3:
> > Add one more check in free_one_page() that checks whether migratetype is
> > MIGRATE_ISOLATE or not. Without this, abovementioned case 1 could happens.
> 
> Good catch.
> 
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> 
> (minor suggestion below)
> 
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -749,9 +749,16 @@ static void free_one_page(struct zone *zone,
> >  	if (nr_scanned)
> >  		__mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
> >  
> > +	if (unlikely(has_isolate_pageblock(zone) ||
> 
> Would it make any difference if this was read just once and not in each
> loop iteration?
> 
> 

I guess that you'd like to say this to patch 2.
I can do it, but, it doesn't any difference in terms of performance,
because we access zone's member variable in each loop iteration
in __free_one_page().

Thanks.
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