[PATCH 1/3] nvme-tcp: avoid inline sending when handling R2T PDUs

[Hannes Reinecke]

When handling an R2T PDU we should not attempt to send consecutive
PDUs as we are running from an softirq context, and sending PDUs
from the receive context will mess up latencies.
So just queue it and let the io_work workqueue function do the work.

Signed-off-by: Hannes Reinecke <hare at kernel.org>
---
 drivers/nvme/host/tcp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 8c14018201db..034edf852878 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -391,7 +391,7 @@ static inline bool nvme_tcp_queue_more(struct nvme_tcp_queue *queue)
 }
 
 static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req,
-		bool sync, bool last)
+		bool last)
 {
 	struct nvme_tcp_queue *queue = req->queue;
 	bool empty;
@@ -405,7 +405,7 @@ static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req,
 	 * are on the same cpu, so we don't introduce contention.
 	 */
 	if (queue->io_cpu == raw_smp_processor_id() &&
-	    sync && empty && mutex_trylock(&queue->send_mutex)) {
+	    empty && mutex_trylock(&queue->send_mutex)) {
 		nvme_tcp_send_all(queue);
 		mutex_unlock(&queue->send_mutex);
 	}
@@ -758,7 +758,9 @@ static int nvme_tcp_handle_r2t(struct nvme_tcp_queue *queue,
 	req->ttag = pdu->ttag;
 
 	nvme_tcp_setup_h2c_data_pdu(req);
-	nvme_tcp_queue_request(req, false, true);
+
+	llist_add(&req->lentry, &queue->req_list);
+	queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work);
 
 	return 0;
 }
@@ -2531,7 +2533,7 @@ static void nvme_tcp_submit_async_event(struct nvme_ctrl *arg)
 	ctrl->async_req.curr_bio = NULL;
 	ctrl->async_req.data_len = 0;
 
-	nvme_tcp_queue_request(&ctrl->async_req, true, true);
+	nvme_tcp_queue_request(&ctrl->async_req, true);
 }
 
 static void nvme_tcp_complete_timed_out(struct request *rq)
@@ -2683,7 +2685,7 @@ static blk_status_t nvme_tcp_queue_rq(struct blk_mq_hw_ctx *hctx,
 
 	nvme_start_request(rq);
 
-	nvme_tcp_queue_request(req, true, bd->last);
+	nvme_tcp_queue_request(req, bd->last);
 
 	return BLK_STS_OK;
 }
-- 
2.35.3