Re: [PATCH] SUNRPC: Fixup v4.1 backchannel request timeouts

[Trond Myklebust <trondmy@hammerspace.com>]

On Fri, 2023-12-08 at 11:33 -0500, Benjamin Coddington wrote:
> After commit 59464b262ff5 ("SUNRPC: SOFTCONN tasks should time out
> when on
> the sending list"), any 4.1 backchannel tasks placed on the sending
> queue
> would immediately return with -ETIMEDOUT since their req timers are
> zero.
> We can fix this by keeping a copy of the rpc_clnt's timeout params on
> the
> transport and using them to properly setup the timeouts on the v4.1
> backchannel tasks' req.
> 
> Fixes: 59464b262ff5 ("SUNRPC: SOFTCONN tasks should time out when on
> the sending list")
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> ---
>  include/linux/sunrpc/xprt.h |  1 +
>  net/sunrpc/clnt.c           |  3 +++
>  net/sunrpc/xprt.c           | 15 +++++++++++++--
>  3 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/sunrpc/xprt.h
> b/include/linux/sunrpc/xprt.h
> index f85d3a0daca2..7565902053f3 100644
> --- a/include/linux/sunrpc/xprt.h
> +++ b/include/linux/sunrpc/xprt.h
> @@ -285,6 +285,7 @@ struct rpc_xprt {
>  						 * items */
>  	struct list_head	bc_pa_list;	/* List of
> preallocated
>  						 * backchannel
> rpc_rqst's */
> +	struct rpc_timeout	bc_timeout;	/* backchannel
> timeout params */
>  #endif /* CONFIG_SUNRPC_BACKCHANNEL */
>  
>  	struct rb_root		recv_queue;	/* Receive queue */
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index d6805c1268a7..5891757c88b1 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -279,6 +279,9 @@ static struct rpc_xprt
> *rpc_clnt_set_transport(struct rpc_clnt *clnt,
>  		clnt->cl_autobind = 1;
>  
>  	clnt->cl_timeout = timeout;
> +#if defined(CONFIG_SUNRPC_BACKCHANNEL)
> +	memcpy(&xprt->bc_timeout, timeout, sizeof(struct
> rpc_timeout));
> +#endif
>  	rcu_assign_pointer(clnt->cl_xprt, xprt);
>  	spin_unlock(&clnt->cl_lock);
>  
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index 92301e32cda4..d9cbe0814fd8 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -655,9 +655,14 @@ static unsigned long
> xprt_abs_ktime_to_jiffies(ktime_t abstime)
>  
>  static unsigned long xprt_calc_majortimeo(struct rpc_rqst *req)
>  {
> -	const struct rpc_timeout *to = req->rq_task->tk_client-
> >cl_timeout;
> +	const struct rpc_timeout *to;
>  	unsigned long majortimeo = req->rq_timeout;
>  
> +	if (req->rq_task->tk_client)
> +		to = req->rq_task->tk_client->cl_timeout;
> +	else
> +		to = &req->rq_xprt->bc_timeout;
> 

If you're going to convert this function for generic use, then please
pass the timeout 'to' as a function parameter rather than making
assumptions here.

> +
>  	if (to->to_exponential)
>  		majortimeo <<= to->to_retries;
>  	else
> @@ -686,7 +691,11 @@ static void xprt_init_majortimeo(struct rpc_task
> *task, struct rpc_rqst *req)
>  		time_init = jiffies;
>  	else
>  		time_init = xprt_abs_ktime_to_jiffies(task-
> >tk_start);
> -	req->rq_timeout = task->tk_client->cl_timeout->to_initval;
> +
> +	if (task->tk_client)
> +		req->rq_timeout = task->tk_client->cl_timeout-
> >to_initval;
> +	else
> +		req->rq_timeout = req->rq_xprt-
> >bc_timeout.to_initval;

Ditto.

>  	req->rq_majortimeo = time_init + xprt_calc_majortimeo(req);
>  	req->rq_minortimeo = time_init + req->rq_timeout;
>  }
> @@ -1998,6 +2007,8 @@ xprt_init_bc_request(struct rpc_rqst *req,
> struct rpc_task *task)
>  	 */
>  	xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
>  		xbufp->tail[0].iov_len;
> +
> +	xprt_init_majortimeo(task, req);
>  }
>  #endif
>  

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com