[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/fs/ntfs/file.c b/fs/ntfs/file.c
index 36e1e136..88292f9 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -231,8 +231,7 @@
 		 * Read the page.  If the page is not present, this will zero
 		 * the uninitialized regions for us.
 		 */
-		page = read_cache_page(mapping, index,
-				(filler_t*)mapping->a_ops->readpage, NULL);
+		page = read_mapping_page(mapping, index, NULL);
 		if (IS_ERR(page)) {
 			err = PTR_ERR(page);
 			goto init_err_out;