mm: Export migrate_page_move_mapping and migrate_page_copy

commit 1118dce7 upstream.

Export these symbols such that UBIFS can implement
->migratepage.
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Christoph Hellwig <hch@lst.de>
[bwh: Backported to 3.2: also change migrate_page_move_mapping() from
 static to extern, done as part of an earlier commit upstream]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/linux/migrate.h

@@ -43,6 +43,9 @@ extern int migrate_vmas(struct mm_struct *mm,
 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
 #define PAGE_MIGRATION 0
 

mm/migrate.c

@@ -294,7 +294,7 @@ static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
  * 2 for pages with a mapping
  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
  */
-static int migrate_page_move_mapping(struct address_space *mapping,
+int migrate_page_move_mapping(struct address_space *mapping,
 		struct page *newpage, struct page *page,
 		struct buffer_head *head, enum migrate_mode mode)
 {
@@ -377,6 +377,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 
 	return 0;
 }
+EXPORT_SYMBOL(migrate_page_move_mapping);
 
 /*
  * The expected number of remaining references is the same as that
@@ -476,6 +477,7 @@ void migrate_page_copy(struct page *newpage, struct page *page)
 	if (PageWriteback(newpage))
 		end_page_writeback(newpage);
 }
+EXPORT_SYMBOL(migrate_page_copy);
 
 /************************************************************
  *                    Migration functions