nvme_req_op
req = blk_mq_alloc_request(q, nvme_req_op(cmd), blk_flags);
req = blk_mq_alloc_request_hctx(q, nvme_req_op(cmd), blk_flags,
rq = blk_mq_alloc_request(ctrl->admin_q, nvme_req_op(&ctrl->ka_cmd),
req = blk_mq_alloc_request(q, nvme_req_op(cmd) | rq_flags, blk_flags);
abort_req = blk_mq_alloc_request(dev->ctrl.admin_q, nvme_req_op(&cmd),
req = blk_mq_alloc_request(q, nvme_req_op(&cmd), BLK_MQ_REQ_NOWAIT);
rq = blk_mq_alloc_request(q, nvme_req_op(req->cmd), 0);