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

Introduce the NVMe-TCP DDP data-path offload.
Using this interface, the NIC hardware will scatter TCP payload directly
to the BIO pages according to the command_id in the PDU.
To maintain the correctness of the network stack, the driver is expected
to construct SKBs that point to the BIO pages.

The data-path interface contains two routines: tcp_ddp_setup/teardown.
The setup provides the mapping from command_id to the request buffers,
while the teardown removes this mapping.

For efficiency, we introduce an asynchronous nvme completion, which is
split between NVMe-TCP and the NIC driver as follows:
NVMe-TCP performs the specific completion, while NIC driver performs the
generic mq_blk completion.

Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Ben Ben-Ishay <benishay@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Yoray Zack <yorayz@mellanox.com>
---
 drivers/nvme/host/tcp.c | 121 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 117 insertions(+), 4 deletions(-)

>   bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags);
> +void nvme_tcp_ddp_teardown_done(void *ddp_ctx);
>   const struct tcp_ddp_ulp_ops nvme_tcp_ddp_ulp_ops __read_mostly = {
> +
>   	.resync_request		= nvme_tcp_resync_request,
> +	.ddp_teardown_done	= nvme_tcp_ddp_teardown_done,
>   };
>   
> +static
> +int nvme_tcp_teardown_ddp(struct nvme_tcp_queue *queue,
> +			  uint16_t command_id,
> +			  struct request *rq)
> +{
> +	struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
> +	struct net_device *netdev = queue->ctrl->offloading_netdev;
> +	int ret;
> +
> +	if (unlikely(!netdev)) {
> +		pr_info_ratelimited("%s: netdev not found\n", __func__);

dev_info_ratelimited

> +		return -EINVAL;
> +	}
> +
> +	ret = netdev->tcp_ddp_ops->tcp_ddp_teardown(netdev, queue->sock->sk,
> +						    &req->ddp, rq);
> +	sg_free_table_chained(&req->ddp.sg_table, SG_CHUNK_SIZE);
> +	req->offloaded = false;
> +	return ret;
> +}
> +
> +void nvme_tcp_ddp_teardown_done(void *ddp_ctx)
> +{
> +	struct request *rq = ddp_ctx;
> +	struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
> +
> +	if (!nvme_try_complete_req(rq, cpu_to_le16(req->status << 1), req->result))
> +		nvme_complete_rq(rq);
> +}
> +
> +static
> +int nvme_tcp_setup_ddp(struct nvme_tcp_queue *queue,
> +		       uint16_t command_id,
> +		       struct request *rq)
> +{
> +	struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
> +	struct net_device *netdev = queue->ctrl->offloading_netdev;
> +	int ret;
> +
> +	req->offloaded = false;
> +
> +	if (unlikely(!netdev)) {
> +		pr_info_ratelimited("%s: netdev not found\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	req->ddp.command_id = command_id;
> +	req->ddp.sg_table.sgl = req->ddp.first_sgl;
> +	ret = sg_alloc_table_chained(&req->ddp.sg_table,
> +		blk_rq_nr_phys_segments(rq), req->ddp.sg_table.sgl,
> +		SG_CHUNK_SIZE);
> +	if (ret)
> +		return -ENOMEM;

newline here

> +	req->ddp.nents = blk_rq_map_sg(rq->q, rq, req->ddp.sg_table.sgl);
> +
> +	ret = netdev->tcp_ddp_ops->tcp_ddp_setup(netdev,
> +						 queue->sock->sk,
> +						 &req->ddp);
> +	if (!ret)
> +		req->offloaded = true;
> +	return ret;
> +}
> +
>   static
>   int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue,
>   			    struct nvme_tcp_config *config)
> @@ -351,6 +422,25 @@ bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags)
>   
>   #else
>   
> +static
> +int nvme_tcp_setup_ddp(struct nvme_tcp_queue *queue,
> +		       uint16_t command_id,
> +		       struct request *rq)
> +{
> +	return -EINVAL;
> +}
> +
> +static
> +int nvme_tcp_teardown_ddp(struct nvme_tcp_queue *queue,
> +			  uint16_t command_id,
> +			  struct request *rq)
> +{
> +	return -EINVAL;
> +}
> +
> +void nvme_tcp_ddp_teardown_done(void *ddp_ctx)
> +{}
> +
>   static
>   int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue,
>   			    struct nvme_tcp_config *config)
> @@ -630,6 +720,7 @@ static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl)
>   static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
>   		struct nvme_completion *cqe)
>   {
> +	struct nvme_tcp_request *req;
>   	struct request *rq;
>   
>   	rq = blk_mq_tag_to_rq(nvme_tcp_tagset(queue), cqe->command_id);
> @@ -641,8 +732,15 @@ static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
>   		return -EINVAL;
>   	}
>   
> -	if (!nvme_try_complete_req(rq, cqe->status, cqe->result))
> -		nvme_complete_rq(rq);
> +	req = blk_mq_rq_to_pdu(rq);
> +	if (req->offloaded) {
> +		req->status = cqe->status;
> +		req->result = cqe->result;
> +		nvme_tcp_teardown_ddp(queue, cqe->command_id, rq);
> +	} else {
> +		if (!nvme_try_complete_req(rq, cqe->status, cqe->result))
> +			nvme_complete_rq(rq);
> +	}
>   	queue->nr_cqe++;
>   
>   	return 0;
> @@ -836,9 +934,18 @@ static int nvme_tcp_recv_pdu(struct nvme_tcp_queue *queue, struct sk_buff *skb,
>   static inline void nvme_tcp_end_request(struct request *rq, u16 status)
>   {
>   	union nvme_result res = {};
> +	struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
> +	struct nvme_tcp_queue *queue = req->queue;
> +	struct nvme_tcp_data_pdu *pdu = (void *)queue->pdu;
>   
> -	if (!nvme_try_complete_req(rq, cpu_to_le16(status << 1), res))
> -		nvme_complete_rq(rq);
> +	if (req->offloaded) {
> +		req->status = cpu_to_le16(status << 1);
> +		req->result = res;
> +		nvme_tcp_teardown_ddp(queue, pdu->command_id, rq);
> +	} else {
> +		if (!nvme_try_complete_req(rq, cpu_to_le16(status << 1), res))
> +			nvme_complete_rq(rq);
> +	}
>   }
>   
>   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?