[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/hfsplus/btree.c b/fs/hfsplus/btree.c
index effa899..cfc852f 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -38,7 +38,7 @@
 		goto free_tree;
 
 	mapping = tree->inode->i_mapping;
-	page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage, NULL);
+	page = read_mapping_page(mapping, 0, NULL);
 	if (IS_ERR(page))
 		goto free_tree;