[PATCH] read_mapping_page for address space

Add read_mapping_page() which is used for callers that pass
mapping->a_ops->readpage as the filler for read_cache_page.  This removes
some duplication from filesystem code.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f2824c3c3..cc367f7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1477,8 +1477,7 @@
 		error = -EINVAL;
 		goto bad_swap;
 	}
-	page = read_cache_page(mapping, 0,
-			(filler_t *)mapping->a_ops->readpage, swap_file);
+	page = read_mapping_page(mapping, 0, swap_file);
 	if (IS_ERR(page)) {
 		error = PTR_ERR(page);
 		goto bad_swap;