1 files changed, 41 insertions, 2 deletions

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index d1473b2e9481..c8778f7e208e 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -60,6 +60,7 @@ out:
                 int migratetype = get_pageblock_migratetype(page);
 
                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
+                zone->nr_isolate_pageblock++;
                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
 
                 __mod_zone_freepage_state(zone, -nr_pages, migratetype);
@@ -75,16 +76,54 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 {
         struct zone *zone;
         unsigned long flags, nr_pages;
+        struct page *isolated_page = NULL;
+        unsigned int order;
+        unsigned long page_idx, buddy_idx;
+        struct page *buddy;
 
         zone = page_zone(page);
         spin_lock_irqsave(&zone->lock, flags);
         if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
                 goto out;
-        nr_pages = move_freepages_block(zone, page, migratetype);
-        __mod_zone_freepage_state(zone, nr_pages, migratetype);
+
+        /*
+         * Because freepage with more than pageblock_order on isolated
+         * pageblock is restricted to merge due to freepage counting problem,
+         * it is possible that there is free buddy page.
+         * move_freepages_block() doesn't care of merge so we need other
+         * approach in order to merge them. Isolation and free will make
+         * these pages to be merged.
+         */
+        if (PageBuddy(page)) {
+                order = page_order(page);
+                if (order >= pageblock_order) {
+                        page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
+                        buddy_idx = __find_buddy_index(page_idx, order);
+                        buddy = page + (buddy_idx - page_idx);
+
+                        if (!is_migrate_isolate_page(buddy)) {
+                                __isolate_free_page(page, order);
+                                set_page_refcounted(page);
+                                isolated_page = page;
+                        }
+                }
+        }
+
+        /*
+         * If we isolate freepage with more than pageblock_order, there
+         * should be no freepage in the range, so we could avoid costly
+         * pageblock scanning for freepage moving.
+         */
+        if (!isolated_page) {
+                nr_pages = move_freepages_block(zone, page, migratetype);
+                __mod_zone_freepage_state(zone, nr_pages, migratetype);
+        }
         set_pageblock_migratetype(page, migratetype);
+        zone->nr_isolate_pageblock--;
 out:
         spin_unlock_irqrestore(&zone->lock, flags);
+        if (isolated_page)
+                __free_pages(isolated_page, order);
 }
 
 static inline struct page *