nvme-tcp: fix H2CData PDU send accounting (again)

We should not access request members after the last send, even to
determine if indeed it was the last data payload send. The reason is
that a completion could have arrived and trigger a new execution of the
request which overridden these members. This was fixed by commit
825619b ("nvme-tcp: fix possible use-after-completion").

Commit e371af0 broke that assumption again to address cases where
multiple r2t pdus are sent per request. To fix it, we need to record the
request data_sent and data_len and after the payload network send we
reference these counters to determine weather we should advance the
request iterator.

Fixes: e371af0 ("nvme-tcp: fix incorrect h2cdata pdu offset accounting")
Reported-by: Keith Busch <[email protected]>
Cc: [email protected] # 5.10+
Signed-off-by: Sagi Grimberg <[email protected]>
Reviewed-by: Keith Busch <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>

Author: sagigrimberg

drivers/nvme/host/tcp.c

@@ -926,12 +926,14 @@ static void nvme_tcp_fail_request(struct nvme_tcp_request *req)
 static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
 {
 	struct nvme_tcp_queue *queue = req->queue;
+	int req_data_len = req->data_len;
 
 	while (true) {
 		struct page *page = nvme_tcp_req_cur_page(req);
 		size_t offset = nvme_tcp_req_cur_offset(req);
 		size_t len = nvme_tcp_req_cur_length(req);
 		bool last = nvme_tcp_pdu_last_send(req, len);
+		int req_data_sent = req->data_sent;
 		int ret, flags = MSG_DONTWAIT;
 
 		if (last && !queue->data_digest && !nvme_tcp_queue_more(queue))
@@ -958,7 +960,7 @@ static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
 		 * in the request where we don't want to modify it as we may
 		 * compete with the RX path completing the request.
 		 */
-		if (req->data_sent + ret < req->data_len)
+		if (req_data_sent + ret < req_data_len)
 			nvme_tcp_advance_req(req, ret);
 
 		/* fully successful last send in current PDU */