[PATCH] RPC: add generic interface for adjusting the congestion window

 A new interface that allows transports to adjust their congestion window
 using the Van Jacobson implementation in xprt.c is provided.

 Test-plan:
 Use WAN simulation to cause sporadic bursty packet loss.  Look for
 significant regression in performance or client stability.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/xprt.h

@@ -258,9 +258,10 @@ void			xprt_set_retrans_timeout_rtt(struct rpc_task *task);
 void			xprt_wake_pending_tasks(struct rpc_xprt *xprt, int status);
 void			xprt_wait_for_buffer_space(struct rpc_task *task);
 void			xprt_write_space(struct rpc_xprt *xprt);
+void			xprt_update_rtt(struct rpc_task *task);
 void			xprt_adjust_cwnd(struct rpc_task *task, int result);
 struct rpc_rqst *	xprt_lookup_rqst(struct rpc_xprt *xprt, u32 xid);
-void			xprt_complete_rqst(struct rpc_xprt *xprt, struct rpc_rqst *req, int copied);
+void			xprt_complete_rqst(struct rpc_task *task, int copied);
 void			xprt_disconnect(struct rpc_xprt *xprt);
 
 /*

net/sunrpc/xprt.c

@@ -591,56 +591,42 @@ struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, u32 xid)
 	return req;
 }
 
+/**
+ * xprt_update_rtt - update an RPC client's RTT state after receiving a reply
+ * @task: RPC request that recently completed
+ *
+ */
+void xprt_update_rtt(struct rpc_task *task)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+	struct rpc_rtt *rtt = task->tk_client->cl_rtt;
+	unsigned timer = task->tk_msg.rpc_proc->p_timer;
+
+	if (timer) {
+		if (req->rq_ntrans == 1)
+			rpc_update_rtt(rtt, timer,
+					(long)jiffies - req->rq_xtime);
+		rpc_set_timeo(rtt, timer, req->rq_ntrans - 1);
+	}
+}
+
 /**
  * xprt_complete_rqst - called when reply processing is complete
- * @xprt: controlling transport
- * @req: RPC request that just completed
+ * @task: RPC request that recently completed
  * @copied: actual number of bytes received from the transport
  *
+ * Caller holds transport lock.
  */
-void xprt_complete_rqst(struct rpc_xprt *xprt, struct rpc_rqst *req, int copied)
-{
-	struct rpc_task	*task = req->rq_task;
-	struct rpc_clnt *clnt = task->tk_client;
-
-	/* Adjust congestion window */
-	if (!xprt->nocong) {
-		unsigned timer = task->tk_msg.rpc_proc->p_timer;
-		xprt_adjust_cwnd(task, copied);
-		if (timer) {
-			if (req->rq_ntrans == 1)
-				rpc_update_rtt(clnt->cl_rtt, timer,
-						(long)jiffies - req->rq_xtime);
-			rpc_set_timeo(clnt->cl_rtt, timer, req->rq_ntrans - 1);
-		}
-	}
+void xprt_complete_rqst(struct rpc_task *task, int copied)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
 
-#ifdef RPC_PROFILE
-	/* Profile only reads for now */
-	if (copied > 1024) {
-		static unsigned long	nextstat;
-		static unsigned long	pkt_rtt, pkt_len, pkt_cnt;
-
-		pkt_cnt++;
-		pkt_len += req->rq_slen + copied;
-		pkt_rtt += jiffies - req->rq_xtime;
-		if (time_before(nextstat, jiffies)) {
-			printk("RPC: %lu %ld cwnd\n", jiffies, xprt->cwnd);
-			printk("RPC: %ld %ld %ld %ld stat\n",
-					jiffies, pkt_cnt, pkt_len, pkt_rtt);
-			pkt_rtt = pkt_len = pkt_cnt = 0;
-			nextstat = jiffies + 5 * HZ;
-		}
-	}
-#endif
+	dprintk("RPC: %5u xid %08x complete (%d bytes received)\n",
+			task->tk_pid, ntohl(req->rq_xid), copied);
 
-	dprintk("RPC: %4d has input (%d bytes)\n", task->tk_pid, copied);
 	list_del_init(&req->rq_list);
 	req->rq_received = req->rq_private_buf.len = copied;
-
-	/* ... and wake up the process. */
 	rpc_wake_up_task(task);
-	return;
 }
 
 static void xprt_timer(struct rpc_task *task)

net/sunrpc/xprtsock.c

@@ -460,8 +460,6 @@ static void xs_udp_data_ready(struct sock *sk, int len)
 		goto out_unlock;
 	task = rovr->rq_task;
 
-	dprintk("RPC: %4d received reply\n", task->tk_pid);
-
 	if ((copied = rovr->rq_private_buf.buflen) > repsize)
 		copied = repsize;
 
@@ -472,7 +470,9 @@ static void xs_udp_data_ready(struct sock *sk, int len)
 	/* Something worked... */
 	dst_confirm(skb->dst);
 
-	xprt_complete_rqst(xprt, rovr, copied);
+	xprt_adjust_cwnd(task, copied);
+	xprt_update_rtt(task);
+	xprt_complete_rqst(task, copied);
 
  out_unlock:
 	spin_unlock(&xprt->transport_lock);
@@ -634,11 +634,8 @@ static inline void xs_tcp_read_request(struct rpc_xprt *xprt, skb_reader_t *desc
 	}
 
 out:
-	if (!(xprt->tcp_flags & XPRT_COPY_DATA)) {
-		dprintk("RPC: %4d received reply complete\n",
-				req->rq_task->tk_pid);
-		xprt_complete_rqst(xprt, req, xprt->tcp_copied);
-	}
+	if (!(xprt->tcp_flags & XPRT_COPY_DATA))
+		xprt_complete_rqst(req->rq_task, xprt->tcp_copied);
 	spin_unlock(&xprt->transport_lock);
 	xs_tcp_check_recm(xprt);
 }