Date: Tue, 28 Oct 2014 16:22:31 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@suse.de>, Johannes Weiner <hannes@cmpxchg.org>,
        Minchan Kim <minchan@kernel.org>,
        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
        Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
        Tang Chen <tangchen@cn.fujitsu.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Wen Congyang <wency@cn.fujitsu.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Michal Nazarewicz <mina86@mina86.com>,
        Laura Abbott <lauraa@codeaurora.org>,
        Heesub Shin <heesub.shin@samsung.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Ritesh Harjani <ritesh.list@gmail.com>, t.stanislaws@samsung.com,
        Gioh Kim <gioh.kim@lge.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v4 1/4] mm/page_alloc: fix incorrect isolation behavior
 by rechecking migratetype
Message-ID: <20141028072231.GC27813@js1304-P5Q-DELUXE>
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 <544E1F70.1030106@suse.cz>
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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@vger.kernel.org>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> Acked-by: Vlastimil Babka <vbabka@suse.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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