expandable RAID-Z

@@ -123,8 +123,9 @@
         NULL,
         vdev_default_asize,
         NULL,                   /* io_start - not applicable to the root */
         NULL,                   /* io_done - not applicable to the root */
         vdev_root_state_change,
+        NULL,
         VDEV_TYPE_ROOT,         /* name of this vdev type */
         B_FALSE                 /* not a leaf vdev */
 };