Hi Olga
On Wed, 2020-07-08 at 17:05 -0400, Olga Kornievskaia wrote:
> Current behaviour: every time a v3 operation is re-sent to the server
> we update (double) the timeout. There is no distinction between
> whether
> or not the previous timer had expired before the re-sent happened.
>
> Here's the scenario:
> 1. Client sends a v3 operation
> 2. Server RST-s the connection (prior to the timeout) (eg.,
> connection
> is immediately reset)
> 3. Client re-sends a v3 operation but the timeout is now 120sec.
>
> As a result, an application sees 2mins pause before a retry in case
> server again does not reply.
>
> Instead, this patch proposes to keep track off when the minor timeout
> should happen and if it didn't, then don't update the new timeout.
>
> Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> ---
> include/linux/sunrpc/xprt.h | 1 +
> net/sunrpc/xprt.c | 11 +++++++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/sunrpc/xprt.h
> b/include/linux/sunrpc/xprt.h
> index e64bd82..a603d48 100644
> --- a/include/linux/sunrpc/xprt.h
> +++ b/include/linux/sunrpc/xprt.h
> @@ -101,6 +101,7 @@ struct rpc_rqst {
> * used in the
> softirq.
> */
> unsigned long rq_majortimeo; /* major timeout
> alarm */
> + unsigned long rq_minortimeo; /* minor timeout
> alarm */
> unsigned long rq_timeout; /* Current timeout
> value */
> ktime_t rq_rtt; /* round-trip time */
> unsigned int rq_retries; /* # of retries */
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index d5cc5db..c0ce232 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -607,6 +607,11 @@ static void xprt_reset_majortimeo(struct
> rpc_rqst *req)
> req->rq_majortimeo += xprt_calc_majortimeo(req);
> }
>
> +static void xprt_reset_minortimeo(struct rpc_rqst *req)
> +{
> + req->rq_minortimeo = jiffies + req->rq_timeout;
> +}
> +
> static void xprt_init_majortimeo(struct rpc_task *task, struct
> rpc_rqst *req)
> {
> unsigned long time_init;
> @@ -618,6 +623,7 @@ static void xprt_init_majortimeo(struct rpc_task
> *task, struct rpc_rqst *req)
> time_init = xprt_abs_ktime_to_jiffies(task->tk_start);
> req->rq_timeout = task->tk_client->cl_timeout->to_initval;
> req->rq_majortimeo = time_init + xprt_calc_majortimeo(req);
> + req->rq_minortimeo = time_init + req->rq_timeout;
> }
>
> /**
> @@ -631,6 +637,10 @@ int xprt_adjust_timeout(struct rpc_rqst *req)
> const struct rpc_timeout *to = req->rq_task->tk_client-
> >cl_timeout;
> int status = 0;
>
> + if (time_before(jiffies, req->rq_minortimeo)) {
> + xprt_reset_minortimeo(req);
> + return status;
Shouldn't this case be just returning without updating the timeout?
After all, this is the case where nothing has expired yet.
> + }
> if (time_before(jiffies, req->rq_majortimeo)) {
> if (to->to_exponential)
> req->rq_timeout <<= 1;
> @@ -638,6 +648,7 @@ int xprt_adjust_timeout(struct rpc_rqst *req)
> req->rq_timeout += to->to_increment;
> if (to->to_maxval && req->rq_timeout >= to->to_maxval)
> req->rq_timeout = to->to_maxval;
> + xprt_reset_minortimeo(req);
...and then perhaps this can just be moved out of the time_before()
condition, since it looks to me as if we also want to reset req-
>rq_minortimeo when a major timeout occurs.
> req->rq_retries++;
> } else {
> req->rq_timeout = to->to_initval;
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
