int dmu_read_req(objset_t *os, uint64_t object, struct request *req);
int dmu_write_req(objset_t *os, uint64_t object, struct request *req,
dmu_tx_t *tx);
int dmu_read_req(objset_t *os, uint64_t object, struct request *req);
int dmu_write_req(objset_t *os, uint64_t object, struct request *req,
dmu_tx_t *tx);