space_map_free
space_map_free(vd->vdev_checkpoint_sm, tx);
space_map_free(sm, tx);
void space_map_free(space_map_t *sm, dmu_tx_t *tx);
space_map_free(vd->vdev_dtl_sm, tx);
space_map_free(vd->vdev_obsolete_sm, tx);