SUNRPC: Fix reconnection timeouts

When the connect attempt fails and backs off, we should start the clock
at the last connection attempt, not time at which we queue up the
reconnect job.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -2173,6 +2173,8 @@ static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock)
 		write_unlock_bh(&sk->sk_callback_lock);
 	}
 	xs_udp_do_set_buffer_size(xprt);
+
+	xprt->stat.connect_start = jiffies;
 }
 
 static void xs_udp_setup_socket(struct work_struct *work)
@@ -2384,6 +2386,16 @@ static void xs_tcp_setup_socket(struct work_struct *work)
 	xprt_wake_pending_tasks(xprt, status);
 }
 
+static unsigned long xs_reconnect_delay(const struct rpc_xprt *xprt)
+{
+	unsigned long start, now = jiffies;
+
+	start = xprt->stat.connect_start + xprt->reestablish_timeout;
+	if (time_after(start, now))
+		return start - now;
+	return 0;
+}
+
 /**
  * xs_connect - connect a socket to a remote endpoint
  * @xprt: pointer to transport structure
@@ -2401,6 +2413,7 @@ static void xs_tcp_setup_socket(struct work_struct *work)
 static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
 {
 	struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
+	unsigned long delay = 0;
 
 	WARN_ON_ONCE(!xprt_lock_connect(xprt, task, transport));
 
@@ -2412,19 +2425,19 @@ static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
 		/* Start by resetting any existing state */
 		xs_reset_transport(transport);
 
-		queue_delayed_work(xprtiod_workqueue,
-				   &transport->connect_worker,
-				   xprt->reestablish_timeout);
+		delay = xs_reconnect_delay(xprt);
+
 		xprt->reestablish_timeout <<= 1;
 		if (xprt->reestablish_timeout < XS_TCP_INIT_REEST_TO)
 			xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
 		if (xprt->reestablish_timeout > XS_TCP_MAX_REEST_TO)
 			xprt->reestablish_timeout = XS_TCP_MAX_REEST_TO;
-	} else {
+	} else
 		dprintk("RPC:       xs_connect scheduled xprt %p\n", xprt);
-		queue_delayed_work(xprtiod_workqueue,
-				   &transport->connect_worker, 0);
-	}
+
+	queue_delayed_work(xprtiod_workqueue,
+			&transport->connect_worker,
+			delay);
 }
 
 /**