zsd_lookup_insert_usage
usage = zsd_lookup_insert_usage(ctl, pset, zone);
prev_usage = zsd_lookup_insert_usage(ctl, prev_pset,
usage = zsd_lookup_insert_usage(ctl, pset, zone);
usage = zsd_lookup_insert_usage(ctl, pset, zone);
usage = zsd_lookup_insert_usage(ctl, pset, zone);