From: Chuck Lever <redacted>

I still see "RPC: Could not send backchannel reply error: -110"
quite often, along with slow-running tests. Debugging shows that the
backchannel is still stumbling when it has to queue a callback reply
on a busy transport.

Note that every one of these timeouts causes a connection loss by
virtue of the xprt_conditional_disconnect() call in that arm of
call_cb_transmit_status().

I found that setting to_maxval is necessary to get the RPC timeout
logic to behave whenever to_exponential is not set.

Fixes: 57331a59ac0d ("NFSv4.1: Use the nfs_client's rpc timeouts for backchannel")
Signed-off-by: Chuck Lever <redacted>
---
 net/sunrpc/svc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 965a27806bfd..f4ddb2961042 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c

@@ -1643,6 +1643,7 @@ void svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp)
 		timeout.to_initval = req->rq_xprt->timeout->to_initval;
 		timeout.to_retries = req->rq_xprt->timeout->to_retries;
 	}
+	timeout.to_maxval = timeout.to_initval;
 	memcpy(&req->rq_snd_buf, &rqstp->rq_res, sizeof(req->rq_snd_buf));
 	task = rpc_run_bc_task(req, &timeout);
 

-- 
2.45.1