nvmet_zero_sgl
nvmet_zero_sgl(req, 0, sizeof(struct nvme_id_ctrl_nvm)));
nvmet_req_complete(req, nvmet_zero_sgl(req, 0, req->transfer_len));
status = nvmet_zero_sgl(req, len, req->transfer_len - len);
u16 nvmet_zero_sgl(struct nvmet_req *req, off_t off, size_t len);