[PATCH v3] mm/page_alloc: fix freeing of MIGRATE_RESERVE migratetype pages

Bartlomiej Zolnierkiewicz
2014-03-06T17:35:31Z

Pages allocated from MIGRATE_RESERVE migratetype pageblocks
are not freed back to MIGRATE_RESERVE migratetype free
lists in free_pcppages_bulk()->__free_one_page() if we got
to free_pcppages_bulk() through drain_[zone_]pages().
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
moving freepage migratetype setting from rmqueue_bulk() to
__rmqueue[_fallback]() and preserving freepage migratetype
as an original pageblock migratetype for MIGRATE_RESERVE
migratetype pages.

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 <b.zolnierkie@samsung.com>
Reported-by: Yong-Taek Lee <ytk.lee@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
---
v2:
- updated patch description, there is no __zone_pcp_update()
in newer kernels
v3:
- set freepage migratetype in __rmqueue[_fallback]()
instead of rmqueue_bulk() (per Mel's request)

mm/page_alloc.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)

Index: b/mm/page_alloc.c
===================================================================
--- a/mm/page_alloc.c 2014-03-06 18:10:21.884422983 +0100
+++ b/mm/page_alloc.c 2014-03-06 18:10:27.016422895 +0100
@@ -1094,7 +1094,7 @@ __rmqueue_fallback(struct zone *zone, in
struct free_area *area;
int current_order;
struct page *page;
- int migratetype, new_type, i;
+ int migratetype, new_type, mt = start_migratetype, i;

/* Find the largest possible block of pages in the other list */
for (current_order = MAX_ORDER-1; current_order >= order;
@@ -1125,6 +1125,14 @@ __rmqueue_fallback(struct zone *zone, in
expand(zone, page, order, current_order, area,
new_type);

+ if (IS_ENABLED(CONFIG_CMA)) {
+ mt = get_pageblock_migratetype(page);
+ if (!is_migrate_cma(mt) &&
+ !is_migrate_isolate(mt))
+ mt = start_migratetype;
+ }
+ set_freepage_migratetype(page, mt);
+
trace_mm_page_alloc_extfrag(page, order, current_order,
start_migratetype, migratetype, new_type);

@@ -1147,7 +1155,9 @@ static struct page *__rmqueue(struct zon
retry_reserve:
page = __rmqueue_smallest(zone, order, migratetype);

- if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
+ if (likely(page)) {
+ set_freepage_migratetype(page, migratetype);
+ } else if (migratetype != MIGRATE_RESERVE) {
page = __rmqueue_fallback(zone, order, migratetype);

/*
@@ -1174,7 +1184,7 @@ static int rmqueue_bulk(struct zone *zon
unsigned long count, struct list_head *list,
int migratetype, int cold)
{
- int mt = migratetype, i;
+ int i;

spin_lock(&zone->lock);
for (i = 0; i < count; ++i) {
@@ -1195,16 +1205,15 @@ static int rmqueue_bulk(struct zone *zon
list_add(&page->lru, list);
else
list_add_tail(&page->lru, list);
+ list = &page->lru;
if (IS_ENABLED(CONFIG_CMA)) {
- mt = get_pageblock_migratetype(page);
+ int mt = get_pageblock_migratetype(page);
if (!is_migrate_cma(mt) && !is_migrate_isolate(mt))
mt = migratetype;
+ if (is_migrate_cma(mt))
+ __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
+ -(1 << order));
}
- set_freepage_migratetype(page, mt);
- list = &page->lru;
- if (is_migrate_cma(mt))
- __mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
- -(1 << order));
}
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
spin_unlock(&zone->lock);