switch {__,}blockdev_direct_IO() to iov_iter

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2b99357..e571838 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3166,8 +3166,8 @@
 		dio_flags = DIO_LOCKING;
 	}
 	ret = __blockdev_direct_IO(rw, iocb, inode,
-				   inode->i_sb->s_bdev, iter->iov,
-				   offset, iter->nr_segs,
+				   inode->i_sb->s_bdev, iter,
+				   offset,
 				   get_block_func,
 				   ext4_end_io_dio,
 				   NULL,