Re: [PATCH v3 net-next 07/21] 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 <redacted>
Signed-off-by: Ben Ben-Ishay <redacted>
Signed-off-by: Or Gerlitz <redacted>
Signed-off-by: Yoray Zack <redacted>
---
  drivers/nvme/host/tcp.c | 141 +++++++++++++++++++++++++++++++++++++---
  1 file changed, 131 insertions(+), 10 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index ea67caf9d326..5cb46deb56e0 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c

@@ -57,6 +57,11 @@ struct nvme_tcp_request {
  	size_t			offset;
  	size_t			data_sent;
  	enum nvme_tcp_send_state state;
+
+	bool			offloaded;
+	struct tcp_ddp_io	ddp;
+	__le16			status;
+	union nvme_result	result;
  };
  
  enum nvme_tcp_queue_flags {

@@ -232,10 +237,74 @@ static inline size_t nvme_tcp_pdu_last_send(struct nvme_tcp_request *req,
  #ifdef CONFIG_TCP_DDP
  
  static bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags);
+static void nvme_tcp_ddp_teardown_done(void *ddp_ctx);
  static const struct tcp_ddp_ulp_ops nvme_tcp_ddp_ulp_ops = {
  	.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,
+			  u16 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__);
+		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 -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;
+	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)
  {

@@ -377,6 +446,25 @@ bool nvme_tcp_resync_request(struct sock *sk, u32 seq, u32 flags)
  
  #else
  
+static
+int nvme_tcp_setup_ddp(struct nvme_tcp_queue *queue,
+		       u16 command_id,
+		       struct request *rq)
+{
+	return -EINVAL;
+}
+
+static
+int nvme_tcp_teardown_ddp(struct nvme_tcp_queue *queue,
+			  u16 command_id,
+			  struct request *rq)
+{
+	return -EINVAL;
+}
+
+static void nvme_tcp_ddp_teardown_done(void *ddp_ctx)
+{}
+
  static
  int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue)
  {

@@ -665,6 +753,7 @@ 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);

@@ -676,8 +765,15 @@ 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;

@@ -871,9 +967,18 @@ 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,

@@ -920,12 +1025,22 @@ static int nvme_tcp_recv_data(struct nvme_tcp_queue *queue, struct sk_buff *skb,
  		recv_len = min_t(size_t, recv_len,
  				iov_iter_count(&req->iter));
  
-		if (queue->data_digest)
-			ret = skb_copy_and_hash_datagram_iter(skb, *offset,
-				&req->iter, recv_len, queue->rcv_hash);
-		else
-			ret = skb_copy_datagram_iter(skb, *offset,
-					&req->iter, recv_len);
+		if (test_bit(NVME_TCP_Q_OFF_DDP, &queue->flags)) {
+			if (queue->data_digest)
+				ret = skb_ddp_copy_and_hash_datagram_iter(skb, *offset,
+						&req->iter, recv_len, queue->rcv_hash);
+			else
+				ret = skb_ddp_copy_datagram_iter(skb, *offset,
+						&req->iter, recv_len);
+		} else {
+			if (queue->data_digest)
+				ret = skb_copy_and_hash_datagram_iter(skb, *offset,
+						&req->iter, recv_len, queue->rcv_hash);
+			else
+				ret = skb_copy_datagram_iter(skb, *offset,
+						&req->iter, recv_len);
+		}
+

  		if (ret) {
  			dev_err(queue->ctrl->ctrl.device,
  				"queue %d failed to copy request %#x data",

@@ -1149,6 +1264,7 @@ 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;
  

@@ -1157,6 +1273,10 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
  	else
  		flags |= MSG_EOR;
  
+	if (test_bit(NVME_TCP_Q_OFF_DDP, &queue->flags) &&
+	    blk_rq_nr_phys_segments(rq) && rq_data_dir(rq) == READ)
+		nvme_tcp_setup_ddp(queue, pdu->cmd.common.command_id, rq);
+
  	if (queue->hdr_digest && !req->offset)
  		nvme_tcp_hdgst(queue->snd_hash, pdu, sizeof(*pdu));
  

@@ -2464,6 +2584,7 @@ static blk_status_t nvme_tcp_setup_cmd_pdu(struct nvme_ns *ns,
  	req->data_len = blk_rq_nr_phys_segments(rq) ?
  				blk_rq_payload_bytes(rq) : 0;
  	req->curr_bio = rq->bio;
+	req->offloaded = false;