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-rw-r--r--mm/page_alloc.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cefe6fe8d99..c54376a09f3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1208,6 +1208,51 @@ void split_page(struct page *page, unsigned int order)
}
/*
+ * Similar to split_page except the page is already free. As this is only
+ * being used for migration, the migratetype of the block also changes.
+ * As this is called with interrupts disabled, the caller is responsible
+ * for calling arch_alloc_page() and kernel_map_page() after interrupts
+ * are enabled.
+ *
+ * Note: this is probably too low level an operation for use in drivers.
+ * Please consult with lkml before using this in your driver.
+ */
+int split_free_page(struct page *page)
+{
+ unsigned int order;
+ unsigned long watermark;
+ struct zone *zone;
+
+ BUG_ON(!PageBuddy(page));
+
+ zone = page_zone(page);
+ order = page_order(page);
+
+ /* Obey watermarks as if the page was being allocated */
+ watermark = low_wmark_pages(zone) + (1 << order);
+ if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ return 0;
+
+ /* Remove page from free list */
+ list_del(&page->lru);
+ zone->free_area[order].nr_free--;
+ rmv_page_order(page);
+ __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
+
+ /* Split into individual pages */
+ set_page_refcounted(page);
+ split_page(page, order);
+
+ if (order >= pageblock_order - 1) {
+ struct page *endpage = page + (1 << order) - 1;
+ for (; page < endpage; page += pageblock_nr_pages)
+ set_pageblock_migratetype(page, MIGRATE_MOVABLE);
+ }
+
+ return 1 << order;
+}
+
+/*
* Really, prep_compound_page() should be called from __rmqueue_bulk(). But
* we cheat by calling it from here, in the order > 0 path. Saves a branch
* or two.