linux-kernel - Re: [PATCH v2 5/5] power: add zone range overlapping check

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Date:	Fri, 1 Apr 2016 10:19:29 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	js1304@...il.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Minchan Kim <minchan@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 5/5] power: add zone range overlapping check

On 1.4.2016 4:06, js1304@...il.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> There is a system that node's pfn are overlapped like as following.
> 
> -----pfn-------->
> N0 N1 N2 N0 N1 N2
> 
> Therefore, we need to care this overlapping when iterating pfn range.
> 
> mark_free_pages() iterates requested zone's pfn range and unset
> all range's bitmap first. And then it marks freepages in a zone
> to the bitmap. If there is an overlapping zone, above unset could
> clear previous marked bit and reference to this bitmap in the future
> will cause the problem. To prevent it, this patch adds a zone check
> in mark_free_pages().
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/page_alloc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0cfee62..437a934 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2156,6 +2156,10 @@ void mark_free_pages(struct zone *zone)
>  	for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
>  		if (pfn_valid(pfn)) {
>  			page = pfn_to_page(pfn);
> +
> +			if (page_zone(page) != zone)
> +				continue;
> +
>  			if (!swsusp_page_is_forbidden(page))
>  				swsusp_unset_page_free(page);
>  		}
>