If (MAX_ORDER-1) is greater than pageblock order, there is a possibility
to merge different migratetype pages and to be linked in unintended
freelist.
While I test CMA, CMA pages are merged and linked into MOVABLE freelist
by above issue and then, the pages change their migratetype to UNMOVABLE by
try_to_steal_freepages(). After that, CMA to this region always fail.
To prevent this, we should not merge the page on MIGRATE_(CMA|ISOLATE)
freelist.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2548b42..ea99cee 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -581,6 +581,15 @@ static inline void __free_one_page(struct page *page,
__mod_zone_freepage_state(zone, 1 << order,
migratetype);
} else {
+ int buddy_mt = get_buddy_migratetype(buddy);
+
+ /* We don't want to merge cma, isolate pages */
+ if (unlikely(order >= pageblock_order) &&
+ migratetype != buddy_mt &&
+ (migratetype >= MIGRATE_PCPTYPES ||
+ buddy_mt >= MIGRATE_PCPTYPES)) {
+ break;
+ }
list_del(&buddy->lru);
zone->free_area[order].nr_free--;
rmv_page_order(buddy);
--
1.7.9.5
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