switch {__,}blockdev_direct_IO() to iov_iter

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 154a6f9..385cce4 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -213,8 +213,7 @@
 	 * FAT need to use the DIO_LOCKING for avoiding the race
 	 * condition of fat_get_block() and ->truncate().
 	 */
-	ret = blockdev_direct_IO(rw, iocb, inode, iter->iov, offset,
-				 iter->nr_segs, fat_get_block);
+	ret = blockdev_direct_IO(rw, iocb, inode, iter, offset, fat_get_block);
 	if (ret < 0 && (rw & WRITE))
 		fat_write_failed(mapping, offset + count);