zrl_is_locked
if (zrl_is_locked(&dnh->dnh_zrlock))
ASSERT(zrl_is_locked(&dnh->dnh_zrlock));
ASSERT(zrl_is_locked(&dnh->dnh_zrlock));
if (!zrl_is_locked(&dn->dn_handle->dnh_zrlock))
extern int zrl_is_locked(zrlock_t *);