fs/aio: Add support to aio ring pages migration

As the aio job will pin the ring pages, that will lead to mem migrated
failed. In order to fix this problem we use an anon inode to manage the aio ring
pages, and  setup the migratepage callback in the anon inode's address space, so
that when mem migrating the aio ring pages will be moved to other mem node safely.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index a405d3dc..c407d88 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -55,6 +55,9 @@
 extern void migrate_page_copy(struct page *newpage, struct page *page);
 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct page *newpage, struct page *page);
+extern int migrate_page_move_mapping(struct address_space *mapping,
+		struct page *newpage, struct page *page,
+		struct buffer_head *head, enum migrate_mode mode);
 #else
 
 static inline void putback_lru_pages(struct list_head *l) {}