expandable RAID-Z

*** 553,560 ****
--- 553,561 ----
          vdev_disk_probe,
          vdev_default_asize,
          vdev_disk_io_start,
          vdev_disk_io_done,
          NULL,
+         NULL,
          VDEV_TYPE_DISK,         /* name of this vdev type */
          B_TRUE                  /* leaf vdev */
  };