[PATCH stable 5.10 03/10] can: isotp: Add error message if txqueuelen is too small

[Oliver Hartkopp <socketcan@hartkopp.net>]

From: Patrick Menschel <menschel.p@posteo.de>

commit c69d190f7bb9a03cf5237d45a457993730d01605 upstream

This patch adds an additional error message in case that txqueuelen is
set too small and advices the user to increase txqueuelen.

This is likely to happen even with small transfers if txqueuelen is at
default value 10 frames.

Link: https://lore.kernel.org/r/20210427052150.2308-4-menschel.p@posteo.de
Signed-off-by: Patrick Menschel <menschel.p@posteo.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 net/can/isotp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index 009d5216f3ea..ef72e5344789 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -811,14 +811,16 @@ static enum hrtimer_restart isotp_tx_timer_handler(struct hrtimer *hrtimer)
 
 		skb->dev = dev;
 		can_skb_set_owner(skb, sk);
 
 		can_send_ret = can_send(skb, 1);
-		if (can_send_ret)
+		if (can_send_ret) {
 			pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
 				       __func__, ERR_PTR(can_send_ret));
-
+			if (can_send_ret == -ENOBUFS)
+				pr_notice_once("can-isotp: tx queue is full, increasing txqueuelen may prevent this error\n");
+		}
 		if (so->tx.idx >= so->tx.len) {
 			/* we are done */
 			so->tx.state = ISOTP_IDLE;
 			dev_put(dev);
 			wake_up_interruptible(&so->wait);
-- 
2.34.1