vdev_open
if (vdev_open(vd) != 0)
if (vdev_open(vd) != 0)
error = vdev_open(spa->spa_root_vdev);
if ((error = vdev_open(vd)) == 0 &&
extern int vdev_open(vdev_t *);
vd->vdev_open_error = vdev_open(vd);
vdev_open(vd->vdev_child[c]);
(void) vdev_open(vd);
error = vdev_open(vd);