[PATCH net-next RFC v1 06/10] nvme-tcp: Add DDP data-path

[Boris Pismenny]

On 09/10/2020 1:29, Sagi Grimberg wrote:
>
>>   static int nvme_tcp_recv_data(struct nvme_tcp_queue *queue, struct sk_buff *skb,
>> @@ -1115,6 +1222,7 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
>>   	bool inline_data = nvme_tcp_has_inline_data(req);
>>   	u8 hdgst = nvme_tcp_hdgst_len(queue);
>>   	int len = sizeof(*pdu) + hdgst - req->offset;
>> +	struct request *rq = blk_mq_rq_from_pdu(req);
>>   	int flags = MSG_DONTWAIT;
>>   	int ret;
>>   
>> @@ -1123,6 +1231,10 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
>>   	else
>>   		flags |= MSG_EOR;
>>   
>> +	if (test_bit(NVME_TCP_Q_OFFLOADS, &queue->flags) &&
>> +	    blk_rq_nr_phys_segments(rq) && rq_data_dir(rq) == READ)
>> +		nvme_tcp_setup_ddp(queue, pdu->cmd.common.command_id, rq);
> I'd assume that this is something we want to setup in
> nvme_tcp_setup_cmd_pdu. Why do it here?
Our goal in placing it here is to keep both setup and teardown in the same thread.
This enables drivers to avoid locking for per-queue operations.