linux-kernel - Re: [RFC 07/16] mm/page_isolation: watch out zone range overlap

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Date:	Fri, 13 Feb 2015 15:40:08 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Joonsoo Kim <iamjoonsoo.kim@....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>,
	Heesub Shin <heesub.shin@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Hui Zhu <zhuhui@...omi.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [RFC 07/16] mm/page_isolation: watch out zone range overlap


> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index c8778f7..883e78d 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -210,8 +210,8 @@ int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>    * Returns 1 if all pages in the range are isolated.
>    */
>   static int
> -__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
> -				  bool skip_hwpoisoned_pages)
> +__test_page_isolated_in_pageblock(struct zone *zone, unsigned long pfn,
> +			unsigned long end_pfn, bool skip_hwpoisoned_pages)
>   {
>   	struct page *page;
>   
> @@ -221,6 +221,9 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
>   			continue;
>   		}
>   		page = pfn_to_page(pfn);
> +		if (page_zone(page) != zone)
> +			break;
> +
>   		if (PageBuddy(page)) {
>   			/*
>   			 * If race between isolatation and allocation happens,
> @@ -281,7 +284,7 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
>   	/* Check all pages are free or marked as ISOLATED */
>   	zone = page_zone(page);
>   	spin_lock_irqsave(&zone->lock, flags);
> -	ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
> +	ret = __test_page_isolated_in_pageblock(zone, start_pfn, end_pfn,
>   						skip_hwpoisoned_pages);
>   	spin_unlock_irqrestore(&zone->lock, flags);
>   	return ret ? 0 : -EBUSY;
> 

What about checking zone at test_pages_isolated?
It might be a little bit early and without locking zone.

@@ -273,8 +273,14 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
         * are not aligned to pageblock_nr_pages.
         * Then we just check migratetype first.
         */
+
+       zone = page_zone(__first_valid_page(start_pfn, pageblock_nr_pages));
+
        for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
                page = __first_valid_page(pfn, pageblock_nr_pages);
+
+               if (page_zone(page) != zone)
+                       break;
                if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
                        break;
        }
--
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