[PATCH v17 06/20] nvme-tcp: Add DDP data-path

Aurelien Aptel
2023-10-24T12:55:48Z

From: Boris Pismenny <borisp@nvidia.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: 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@nvidia.com>
Signed-off-by: Ben Ben-Ishay <benishay@nvidia.com>
Signed-off-by: Or Gerlitz <ogerlitz@nvidia.com>
Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Shai Malin <smalin@nvidia.com>
Signed-off-by: Aurelien Aptel <aaptel@nvidia.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
---
drivers/nvme/host/tcp.c | 111 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 106 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 387093cb0ca6..8ad03670eeb5 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -112,6 +112,13 @@ struct nvme_tcp_request {
size_t offset;
size_t data_sent;
enum nvme_tcp_send_state state;
+
+#ifdef CONFIG_ULP_DDP
+ bool offloaded;
+ struct ulp_ddp_io ddp;
+ __le16 ddp_status;
+ union nvme_result result;
+#endif
};

enum nvme_tcp_queue_flags {
@@ -336,10 +343,72 @@ nvme_tcp_get_ddp_netdev_with_limits(struct nvme_tcp_ctrl *ctrl)
}

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 ulp_ddp_ulp_ops nvme_tcp_ddp_ulp_ops = {
.resync_request = nvme_tcp_resync_request,
+ .ddp_teardown_done = nvme_tcp_ddp_teardown_done,
};

+static void nvme_tcp_teardown_ddp(struct nvme_tcp_queue *queue,
+ struct request *rq)
+{
+ struct net_device *netdev = queue->ctrl->ddp_netdev;
+ struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
+
+ ulp_ddp_teardown(netdev, queue->sock->sk, &req->ddp, rq);
+ sg_free_table_chained(&req->ddp.sg_table, SG_CHUNK_SIZE);
+}
+
+static 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, req->ddp_status, req->result))
+ nvme_complete_rq(rq);
+}
+
+static void nvme_tcp_setup_ddp(struct nvme_tcp_queue *queue,
+ struct request *rq)
+{
+ struct net_device *netdev = queue->ctrl->ddp_netdev;
+ struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
+ int ret;
+
+ if (rq_data_dir(rq) != READ ||
+ queue->ctrl->ddp_threshold > blk_rq_payload_bytes(rq))
+ return;
+
+ /*
+ * DDP offload is best-effort, errors are ignored.
+ */
+
+ req->ddp.command_id = nvme_cid(rq);
+ 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)
+ goto err;
+ req->ddp.nents = blk_rq_map_sg(rq->q, rq, req->ddp.sg_table.sgl);
+
+ ret = ulp_ddp_setup(netdev, queue->sock->sk, &req->ddp);
+ if (ret) {
+ sg_free_table_chained(&req->ddp.sg_table, SG_CHUNK_SIZE);
+ goto err;
+ }
+
+ /* if successful, sg table is freed in nvme_tcp_teardown_ddp() */
+ req->offloaded = true;
+
+ return;
+err:
+ WARN_ONCE(ret, "ddp setup failed (queue 0x%x, cid 0x%x, ret=%d)",
+ nvme_tcp_queue_id(queue),
+ nvme_cid(rq),
+ ret);
+}
+
static int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue)
{
struct ulp_ddp_config config = {.type = ULP_DDP_NVME};
@@ -460,6 +529,10 @@ static int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue)
static void nvme_tcp_unoffload_socket(struct nvme_tcp_queue *queue)
{}

+static void nvme_tcp_setup_ddp(struct nvme_tcp_queue *queue,
+ struct request *rq)
+{}
+
static void nvme_tcp_resync_response(struct nvme_tcp_queue *queue,
struct sk_buff *skb, unsigned int offset)
{}
@@ -735,6 +808,26 @@ static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl)
queue_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work);
}

+static void nvme_tcp_complete_request(struct request *rq,
+ __le16 status,
+ union nvme_result result,
+ __u16 command_id)
+{
+#ifdef CONFIG_ULP_DDP
+ struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
+
+ if (req->offloaded) {
+ req->ddp_status = status;
+ req->result = result;
+ nvme_tcp_teardown_ddp(req->queue, rq);
+ return;
+ }
+#endif
+
+ if (!nvme_try_complete_req(rq, status, result))
+ nvme_complete_rq(rq);
+}
+
static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
struct nvme_completion *cqe)
{
@@ -754,10 +847,9 @@ static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
if (req->status == cpu_to_le16(NVME_SC_SUCCESS))
req->status = cqe->status;

- if (!nvme_try_complete_req(rq, req->status, cqe->result))
- nvme_complete_rq(rq);
+ nvme_tcp_complete_request(rq, req->status, cqe->result,
+ cqe->command_id);
queue->nr_cqe++;
-
return 0;
}

@@ -955,10 +1047,13 @@ 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)
{
+ 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;
union nvme_result res = {};

- if (!nvme_try_complete_req(rq, cpu_to_le16(status << 1), res))
- nvme_complete_rq(rq);
+ nvme_tcp_complete_request(rq, cpu_to_le16(status << 1), res,
+ pdu->command_id);
}

static int nvme_tcp_recv_data(struct nvme_tcp_queue *queue, struct sk_buff *skb,
@@ -1265,6 +1360,9 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
else
msg.msg_flags |= MSG_EOR;

+ if (test_bit(NVME_TCP_Q_OFF_DDP, &queue->flags))
+ nvme_tcp_setup_ddp(queue, blk_mq_rq_from_pdu(req));
+
if (queue->hdr_digest && !req->offset)
nvme_tcp_hdgst(queue->snd_hash, pdu, sizeof(*pdu));

@@ -2566,6 +2664,9 @@ static blk_status_t nvme_tcp_setup_cmd_pdu(struct nvme_ns *ns,
if (ret)
return ret;

+#ifdef CONFIG_ULP_DDP
+ req->offloaded = false;
+#endif
req->state = NVME_TCP_SEND_CMD_PDU;
req->status = cpu_to_le16(NVME_SC_SUCCESS);
req->offset = 0;
--
2.34.1