> On Jan 3, 2019, at 11:05 AM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote:
>
> On Thu, 2019-01-03 at 10:29 -0500, Chuck Lever wrote:
>> Hi Trond-
>>
>> I was curious about this one because yesterday I saw evidence (for
>> other reasons) that rq_bytes_sent wasn't always zeroed when it should
>> be.
>>
>>
>>> On Jan 2, 2019, at 5:53 PM, Trond Myklebust <trondmy@xxxxxxxxx>
>>> wrote:
>>>
>>> When we resend a request, ensure that the 'rq_bytes_sent' is reset
>>> to zero.
>>>
>>> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>>> ---
>>> net/sunrpc/clnt.c | 1 -
>>> net/sunrpc/xprt.c | 1 +
>>> 2 files changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
>>> index 24cbddc44c88..2189fbc4c570 100644
>>> --- a/net/sunrpc/clnt.c
>>> +++ b/net/sunrpc/clnt.c
>>> @@ -1738,7 +1738,6 @@ rpc_xdr_encode(struct rpc_task *task)
>>> xdr_buf_init(&req->rq_rcv_buf,
>>> req->rq_rbuffer,
>>> req->rq_rcvsize);
>>> - req->rq_bytes_sent = 0;
>>
>> I agree this line is not sufficient, and it should be moved.
>> Not every retransmission requires a re-encode. However, the
>> patch description should explain that, and it probably needs
>> a Fixes: tag.
>>
>> Can you now also remove the same line from xprt_request_init
>> and xprt_init_bc_request ?
>>
>> Also, I notice that UDP does not touch rq_bytes_sent. Since
>> RDMA also does not use rq_bytes_sent, maybe the same line
>> can be removed from xprtrdma/transport.c and
>> xprtrdma/backchannel.c ?
>
> Sure.
>
> So please note that rq_bytes_sent == 0 no longer means "this request
> needs to be retransmitted" and we no longer test for it in
> net/sunrpc/clnt.c. We do still have a couple of tests of rq_bytes_sent
> in net/sunrpc/xprt.c and net/sunrpc/xprtsock.c, but those are more
> about checking if a transmission of that request is currently in
> progress, in which case we don't want to queue anything in front of it
> on the transmission queue, and we don't want to abort the transmission
> unless we also close the socket.
>
> The intention now is that if we know the request needs retransmission
> (due to a transport connection loss or a timeout), then we just add it
> to the transmission queue.
>
>
>>> p = rpc_encode_header(task);
>>> if (p == NULL) {
>>> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
>>> index 73547d17d3c6..9075ae150ae5 100644
>>> --- a/net/sunrpc/xprt.c
>>> +++ b/net/sunrpc/xprt.c
>>> @@ -1151,6 +1151,7 @@ xprt_request_enqueue_transmit(struct rpc_task
>>> *task)
>>> struct rpc_xprt *xprt = req->rq_xprt;
>>>
>>> if (xprt_request_need_enqueue_transmit(task, req)) {
>>> + req->rq_bytes_sent = 0;
>>> spin_lock(&xprt->queue_lock);
>>> /*
>>> * Requests that carry congestion control credits are
>>> added
>>
>> So I'm not convinced this covers every case. I need some
>> time to investigate.
>
> It should normally cover all cases. As I said, the only remaining tests
> are in xprt.c and xprtsock.c
In the patch I have that removes xprt::tsh_size, I'm using rq_bytes_sent
to figure out when to insert a record marker. Every once in a while, it
sticks in a record marker where it shouldn't.
--
Chuck Lever
