mm/page_alloc: fix freeing of MIGRATE_RESERVE migratetype pages

RFC PATCH Superseded Bartlomiej Zolnierkiewicz 1 participant 1 message Feb 14, 2014

Subsystems (4)

Memory management MM core Page allocator MGLRU

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Bartlomiej Zolnierkiewicz

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2014-02-14 18:08 UTC #0 lore raw

RFC PATCH 1/1 mm/page_alloc: fix freeing of MIGRATE_RESERVE migratetype pages

Pages allocated from MIGRATE_RESERVE migratetype pageblocks are not freed back to MIGRATE_RESERVE migratetype free lists in free_pcppages_bulk() if we got to that function through drain_[zone_]pages() or __zone_pcp_update(). The freeing through free_hot_cold_page() is okay because freepage migratetype is set to pageblock migratetype before calling free_pcppages_bulk(). If pages of MIGRATE_RESERVE migratetype end up on the free lists of other migratetype whole Reserved pageblock may be later changed to the other migratetype in __rmqueue_fallback() and it will be never changed back to be a Reserved pageblock. Fix the issue by preserving freepage migratetype as a pageblock migratetype (instead of overriding it to the requested migratetype) for MIGRATE_RESERVE migratetype pages in rmqueue_bulk().

The problem was introduced in v2.6.31 by commit ed0ae21 ("page allocator: do not call get_pageblock_migratetype() more than necessary").

Signed-off-by Bartlomiej Zolnierkiewicz <[email protected]>

Reported-by Yong-Taek Lee <[email protected]>

Cc Marek Szyprowski <[email protected]>

Cc Mel Gorman <[email protected]>

Cc Hugh Dickins <[email protected]>

---
 include/linux/mmzone.h |    5 +++++
 mm/page_alloc.c        |   10 +++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

include/linux/mmzone.h +5 -0

Index: b/include/linux/mmzone.h
===================================================================
@@ -63,6 +63,11 @@ enum {
 	MIGRATE_TYPES
 };
 
+static inline bool is_migrate_reserve(int migratetype)
+{
+	return unlikely(migratetype == MIGRATE_RESERVE);
+}
+
 #ifdef CONFIG_CMA
 #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
 #else

mm/page_alloc.c +7 -3

Index: b/mm/page_alloc.c
===================================================================
@@ -1174,7 +1174,7 @@ static int rmqueue_bulk(struct zone *zon
 			unsigned long count, struct list_head *list,
 			int migratetype, int cold)
 {
-	int mt = migratetype, i;
+	int mt, i;
 
 	spin_lock(&zone->lock);
 	for (i = 0; i < count; ++i) {

@@ -1195,9 +1195,13 @@ static int rmqueue_bulk(struct zone *zon
 			list_add(&page->lru, list);
 		else
 			list_add_tail(&page->lru, list);
+		mt = get_pageblock_migratetype(page);
 		if (IS_ENABLED(CONFIG_CMA)) {
-			mt = get_pageblock_migratetype(page);
-			if (!is_migrate_cma(mt) && !is_migrate_isolate(mt))
+			if (!is_migrate_cma(mt) && !is_migrate_isolate(mt) &&
+			    !is_migrate_reserve(mt))
+				mt = migratetype;
+		} else {
+			if (!is_migrate_reserve(mt))
 				mt = migratetype;
 		}
 		set_freepage_migratetype(page, mt);