spa_guid_exists
spa_guid_exists(pool_guid, 0)) {
spa_guid_exists(pool_guid, 0) &&
while (guid == 0 || spa_guid_exists(spa_guid(spa), guid))
while (guid == 0 || spa_guid_exists(guid, 0))
extern boolean_t spa_guid_exists(uint64_t pool_guid, uint64_t device_guid);
ASSERT(!spa_guid_exists(spa_guid(spa), guid));
!spa_guid_exists(pool_guid, device_guid) &&