linux-kernel - Re: [PATCH 1/7] mm/page_alloc: synchronize get/set pageblock

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Date:	Thu, 09 Jan 2014 10:08:10 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Jiang Liu <jiang.liu@...wei.com>, Mel Gorman <mgorman@...e.de>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Tang Chen <tangchen@...fujitsu.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 1/7] mm/page_alloc: synchronize get/set pageblock

On Thu, Jan 09 2014, Joonsoo Kim wrote:
> @@ -5927,15 +5928,19 @@ unsigned long get_pageblock_flags_group(struct page *page,
>  	unsigned long pfn, bitidx;
>  	unsigned long flags = 0;
>  	unsigned long value = 1;
> +	unsigned int seq;
>  
>  	zone = page_zone(page);
>  	pfn = page_to_pfn(page);
>  	bitmap = get_pageblock_bitmap(zone, pfn);
>  	bitidx = pfn_to_bitidx(zone, pfn);
>  
> -	for (; start_bitidx <= end_bitidx; start_bitidx++, value <<= 1)
> -		if (test_bit(bitidx + start_bitidx, bitmap))
> -			flags |= value;
> +	do {

+		flags = 0;

> +		seq = read_seqbegin(&zone->pageblock_seqlock);
> +		for (; start_bitidx <= end_bitidx; start_bitidx++, value <<= 1)
> +			if (test_bit(bitidx + start_bitidx, bitmap))
> +				flags |= value;
> +	} while (read_seqretry(&zone->pageblock_seqlock, seq));
>  
>  	return flags;
>  }

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--


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