On Thu, Jun 20, 2024 at 07:41:21AM -0400, Benjamin Coddington wrote:
> On 19 Jun 2024, at 9:51, cel@xxxxxxxxxx wrote:
>
> > From: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >
> > 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 <chuck.lever@xxxxxxxxxx>
>
> That makes sense - I guess we were getting some random stack value in there?
Hi Ben-
On my systems it was always zero (which is why v1 of this patch did
not clear the other fields in @timeout before using it).
A zero to_maxval value results in the same timeout-on-sleep behavior
as you saw before 57331a59ac0d was applied.
A random non-zero value will behave correctly as long as the transport
is making forward progress, so we never noticed a problem.
> Reviewed-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
>
> Ben
>
> > ---
> > net/sunrpc/svc.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> > index 965a27806bfd..e03f14024e47 100644
> > --- a/net/sunrpc/svc.c
> > +++ b/net/sunrpc/svc.c
> > @@ -1588,9 +1588,11 @@ void svc_process(struct svc_rqst *rqstp)
> > */
> > void svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp)
> > {
> > + struct rpc_timeout timeout = {
> > + .to_increment = 0,
> > + };
> > struct rpc_task *task;
> > int proc_error;
> > - struct rpc_timeout timeout;
> >
> > /* Build the svc_rqst used by the common processing routine */
> > rqstp->rq_xid = req->rq_xid;
> > @@ -1643,6 +1645,7 @@ 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
>
--
Chuck Lever
