[PATCH v2] nvme-tcp: send quota for nvme_tcp_send_all()

[Daniel Wagner <dwagner@suse.de>]

Add a send quota in nvme_tcp_send_all() to avoid stalls when sending
large amounts of requests.

Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
---

IMO, this patch might still be a good idea to add. At least in my test
setup where I only have one ethernet port it makes a big difference
when accessing the system via ssh. When nvme-tcp is pushing a lot of
data via the network, the ssh session is completely blocked by the
storage traffic. With it, the ssh session stays responsive.

I suspect a proper storage setup would use more than one ethernet
port.

Daniel

v1:
  https://lore.kernel.org/linux-nvme/20220519062617.39715-4-hare@suse.de/

 drivers/nvme/host/tcp.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 3e7b29d07c71..84a66ca208c8 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -308,12 +308,23 @@ static inline void nvme_tcp_advance_req(struct nvme_tcp_request *req,
 
 static inline void nvme_tcp_send_all(struct nvme_tcp_queue *queue)
 {
-	int ret;
+	unsigned long deadline = jiffies + msecs_to_jiffies(1);
 
 	/* drain the send queue as much as we can... */
 	do {
-		ret = nvme_tcp_try_send(queue);
-	} while (ret > 0);
+		bool pending = false;
+		int result;
+
+		result = nvme_tcp_try_send(queue);
+		if (result > 0)
+			pending = true;
+		else if (unlikely(result < 0))
+			return;
+
+		if (!pending)
+			return;
+
+	} while (!time_after(jiffies, deadline)); /* quota is exhausted */
 }
 
 static inline bool nvme_tcp_queue_more(struct nvme_tcp_queue *queue)
-- 
2.38.0