Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\))
Subject: Re: [PATCH 1/4] SUNRPC: Ensure rq_bytes_sent is reset before request
 transmission
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20190102225313.2097-2-trond.myklebust@hammerspace.com>
Date:   Thu, 3 Jan 2019 10:29:33 -0500
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Transfer-Encoding: 7bit
Message-Id: <1B5E1F96-246A-43AB-B9CE-FA41C595ADFF@oracle.com>
References: <20190102225313.2097-1-trond.myklebust@hammerspace.com>
 <20190102225313.2097-2-trond.myklebust@hammerspace.com>
To:     Trond Myklebust <trondmy@gmail.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

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@gmail.com> wrote:
> 
> When we resend a request, ensure that the 'rq_bytes_sent' is reset
> to zero.
> 
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
> ---
> 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 ?


> 	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.


--
Chuck Lever