+/*
+ * If breaking a large block of pages, move all free pages to the preferred
+ * allocation list. If falling back for a reclaimable kernel allocation, be
+ * more aggressive about taking ownership of free pages.
+ *
+ * On the other hand, never change migration type of MIGRATE_CMA pageblocks
+ * nor move CMA pages to different free lists. We don't want unmovable pages
+ * to be allocated from MIGRATE_CMA areas.
+ *
+ * Returns the new migratetype of the pageblock (or the same old migratetype
+ * if it was unchanged).
+ */
+static int try_to_steal_freepages(struct zone *zone, struct page *page,
+ int start_type, int fallback_type)
+{
+ int current_order = page_order(page);
+
+ if (is_migrate_cma(fallback_type))
+ return fallback_type;
+
+ /* Take ownership for orders >= pageblock_order */
+ if (current_order >= pageblock_order) {
+ change_pageblock_range(page, current_order, start_type);
+ return start_type;
+ }
+
+ if (current_order >= pageblock_order / 2 ||
+ start_type == MIGRATE_RECLAIMABLE ||
+ page_group_by_mobility_disabled) {
+ int pages;
+
+ pages = move_freepages_block(zone, page, start_type);
+
+ /* Claim the whole block if over half of it is free */
+ if (pages >= (1 << (pageblock_order-1)) ||
+ page_group_by_mobility_disabled) {
+
+ set_pageblock_migratetype(page, start_type);
+ return start_type;
+ }
+
+ }
+
+ return fallback_type;
+}
+