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

[kosaki . motohiro]

From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
 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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