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Commit 15748048 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

vmscan: avoid subtraction of unsigned types 



'slab_reclaimable' and 'nr_pages' are unsigned.  Subtraction is unsafe
because negative results would be misinterpreted.

Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7ee92255

mm/vmscan.c

+8 −7
Original line number Diff line number Diff line
@@ -2600,7 +2600,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
		.swappiness = vm_swappiness,

		.order = order,

	};

	unsigned long slab_reclaimable;

	unsigned long nr_slab_pages0, nr_slab_pages1;



	cond_resched();

	/*
@@ -2625,8 +2625,8 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
		} while (priority >= 0 && sc.nr_reclaimed < nr_pages);

	}



	slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);

	if (slab_reclaimable > zone->min_slab_pages) {

	nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);

	if (nr_slab_pages0 > zone->min_slab_pages) {

		/*

		 * shrink_slab() does not currently allow us to determine how

		 * many pages were freed in this zone. So we take the current
@@ -2638,16 +2638,17 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
		 * take a long time.

		 */

		while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&

			zone_page_state(zone, NR_SLAB_RECLAIMABLE) >

				slab_reclaimable - nr_pages)

		       (zone_page_state(zone, NR_SLAB_RECLAIMABLE) + nr_pages >

				nr_slab_pages0))

			;



		/*

		 * Update nr_reclaimed by the number of slab pages we

		 * reclaimed from this zone.

		 */

		sc.nr_reclaimed += slab_reclaimable -

			zone_page_state(zone, NR_SLAB_RECLAIMABLE);

		nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);

		if (nr_slab_pages1 < nr_slab_pages0)

			sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;

	}



	p->reclaim_state = NULL;