[PATCH v1 net-next 06/15] nvme-tcp: Add DDP data-path

[Boris Pismenny <borisp@mellanox.com>]

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 | 119 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 115 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index ef96e4a02bbd..534fd5c00f33 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 {
@@ -231,10 +236,74 @@ static inline size_t nvme_tcp_pdu_last_send(struct nvme_tcp_request *req,
 #ifdef CONFIG_TCP_DDP
 
 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 = {
 	.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 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,
+		       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;
+
+	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;
+	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)
 {
@@ -374,6 +443,25 @@ 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;
+}
+
+void nvme_tcp_ddp_teardown_done(void *ddp_ctx)
+{}
+
 static
 int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue)
 {
@@ -651,6 +739,7 @@ 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);
@@ -662,8 +751,15 @@ 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;
@@ -857,9 +953,18 @@ 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,
@@ -1135,6 +1240,7 @@ 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;
 
@@ -1143,6 +1249,10 @@ 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);
+
 	if (queue->hdr_digest && !req->offset)
 		nvme_tcp_hdgst(queue->snd_hash, pdu, sizeof(*pdu));
 
@@ -2445,6 +2555,7 @@ 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;
 
 	if (rq_data_dir(rq) == WRITE &&
 	    req->data_len <= nvme_tcp_inline_data_size(queue))
-- 
2.24.1