linux-kernel - [PATCH] mm: clear pages_scanned only if draining a pcp adds pages to the buddy allocator again

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Date:	Thu, 14 Jun 2012 12:16:10 -0400
From:	kosaki.motohiro@...il.com
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, akpm@...ux-foundation.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>
Subject: [PATCH] mm: clear pages_scanned only if draining a pcp adds pages to the buddy allocator again

From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

commit 2ff754fa8f (mm: clear pages_scanned only if draining a pcp adds pages
to the buddy allocator again) fixed one free_pcppages_bulk() misuse. But two
another miuse still exist.

This patch fixes it.

Cc: David Rientjes <rientjes@...gle.com>
Cc: Mel Gorman <mel@....ul.ie>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Minchan Kim <minchan.kim@...il.com>
Cc: Wu Fengguang <fengguang.wu@...el.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 mm/page_alloc.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5716b00..4e7059d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1157,8 +1157,10 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
 		to_drain = pcp->batch;
 	else
 		to_drain = pcp->count;
-	free_pcppages_bulk(zone, to_drain, pcp);
-	pcp->count -= to_drain;
+	if (to_drain > 0) {
+		free_pcppages_bulk(zone, to_drain, pcp);
+		pcp->count -= to_drain;
+	}
 	local_irq_restore(flags);
 }
 #endif
@@ -3914,7 +3916,8 @@ static int __zone_pcp_update(void *data)
 		pcp = &pset->pcp;
 
 		local_irq_save(flags);
-		free_pcppages_bulk(zone, pcp->count, pcp);
+		if (pcp->count > 0)
+			free_pcppages_bulk(zone, pcp->count, pcp);
 		setup_pageset(pset, batch);
 		local_irq_restore(flags);
 	}
-- 
1.7.1

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