pass iov_iter to ->direct_IO()

unmodified, for now

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d7b7462..f51db73 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3222,8 +3222,7 @@
 }
 
 static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb,
-			      const struct iovec *iov, loff_t offset,
-			      unsigned long nr_segs)
+			      struct iov_iter *iter, loff_t offset)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
@@ -3239,13 +3238,13 @@
 	if (ext4_has_inline_data(inode))
 		return 0;
 
-	trace_ext4_direct_IO_enter(inode, offset, iov_length(iov, nr_segs), rw);
+	trace_ext4_direct_IO_enter(inode, offset, iov_length(iter->iov, iter->nr_segs), rw);
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-		ret = ext4_ext_direct_IO(rw, iocb, iov, offset, nr_segs);
+		ret = ext4_ext_direct_IO(rw, iocb, iter->iov, offset, iter->nr_segs);
 	else
-		ret = ext4_ind_direct_IO(rw, iocb, iov, offset, nr_segs);
+		ret = ext4_ind_direct_IO(rw, iocb, iter->iov, offset, iter->nr_segs);
 	trace_ext4_direct_IO_exit(inode, offset,
-				iov_length(iov, nr_segs), rw, ret);
+				iov_length(iter->iov, iter->nr_segs), rw, ret);
 	return ret;
 }