SUNRPC: Add a transmission queue for RPC requests

Add the queue that will enforce the ordering of RPC task transmission.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/xprt.h

@@ -88,6 +88,8 @@ struct rpc_rqst {
 		struct list_head	rq_recv;	/* Receive queue */
 	};
 
+	struct list_head	rq_xmit;	/* Send queue */
+
 	void			*rq_buffer;	/* Call XDR encode buffer */
 	size_t			rq_callsize;
 	void			*rq_rbuffer;	/* Reply XDR decode buffer */
@@ -242,6 +244,9 @@ struct rpc_xprt {
 	spinlock_t		queue_lock;	/* send/receive queue lock */
 	u32			xid;		/* Next XID value to use */
 	struct rpc_task *	snd_task;	/* Task blocked in send */
+
+	struct list_head	xmit_queue;	/* Send queue */
+
 	struct svc_xprt		*bc_xprt;	/* NFSv4.1 backchannel */
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 	struct svc_serv		*bc_serv;       /* The RPC service which will */
@@ -339,6 +344,7 @@ void			xprt_free_slot(struct rpc_xprt *xprt,
 				       struct rpc_rqst *req);
 void			xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
 bool			xprt_prepare_transmit(struct rpc_task *task);
+void			xprt_request_enqueue_transmit(struct rpc_task *task);
 void			xprt_request_enqueue_receive(struct rpc_task *task);
 void			xprt_request_wait_receive(struct rpc_task *task);
 void			xprt_transmit(struct rpc_task *task);

net/sunrpc/clnt.c

@@ -1156,11 +1156,11 @@ struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req)
 	 */
 	xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
 			xbufp->tail[0].iov_len;
-	set_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
 
 	task->tk_action = call_bc_transmit;
 	atomic_inc(&task->tk_count);
 	WARN_ON_ONCE(atomic_read(&task->tk_count) != 2);
+	xprt_request_enqueue_transmit(task);
 	rpc_execute(task);
 
 	dprintk("RPC: rpc_run_bc_task: task= %p\n", task);
@@ -1759,8 +1759,6 @@ rpc_xdr_encode(struct rpc_task *task)
 
 	task->tk_status = rpcauth_wrap_req(task, encode, req, p,
 			task->tk_msg.rpc_argp);
-	if (task->tk_status == 0)
-		set_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
 }
 
 /*
@@ -1964,6 +1962,7 @@ call_transmit(struct rpc_task *task)
 	/* Add task to reply queue before transmission to avoid races */
 	if (rpc_reply_expected(task))
 		xprt_request_enqueue_receive(task);
+	xprt_request_enqueue_transmit(task);
 
 	if (!xprt_prepare_transmit(task))
 		return;
@@ -1998,7 +1997,6 @@ call_transmit_status(struct rpc_task *task)
 		xprt_end_transmit(task);
 		break;
 	case -EBADMSG:
-		clear_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
 		task->tk_action = call_transmit;
 		task->tk_status = 0;
 		xprt_end_transmit(task);

net/sunrpc/xprt.c

@@ -1058,6 +1058,72 @@ void xprt_request_wait_receive(struct rpc_task *task)
 	spin_unlock(&xprt->queue_lock);
 }
 
+static bool
+xprt_request_need_transmit(struct rpc_task *task)
+{
+	return !(task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT) ||
+		xprt_request_retransmit_after_disconnect(task);
+}
+
+static bool
+xprt_request_need_enqueue_transmit(struct rpc_task *task, struct rpc_rqst *req)
+{
+	return xprt_request_need_transmit(task) &&
+		!test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
+}
+
+/**
+ * xprt_request_enqueue_transmit - queue a task for transmission
+ * @task: pointer to rpc_task
+ *
+ * Add a task to the transmission queue.
+ */
+void
+xprt_request_enqueue_transmit(struct rpc_task *task)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+	struct rpc_xprt *xprt = req->rq_xprt;
+
+	if (xprt_request_need_enqueue_transmit(task, req)) {
+		spin_lock(&xprt->queue_lock);
+		list_add_tail(&req->rq_xmit, &xprt->xmit_queue);
+		set_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
+		spin_unlock(&xprt->queue_lock);
+	}
+}
+
+/**
+ * xprt_request_dequeue_transmit_locked - remove a task from the transmission queue
+ * @task: pointer to rpc_task
+ *
+ * Remove a task from the transmission queue
+ * Caller must hold xprt->queue_lock
+ */
+static void
+xprt_request_dequeue_transmit_locked(struct rpc_task *task)
+{
+	xprt_task_clear_bytes_sent(task);
+	if (test_and_clear_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
+		list_del(&task->tk_rqstp->rq_xmit);
+}
+
+/**
+ * xprt_request_dequeue_transmit - remove a task from the transmission queue
+ * @task: pointer to rpc_task
+ *
+ * Remove a task from the transmission queue
+ */
+static void
+xprt_request_dequeue_transmit(struct rpc_task *task)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+	struct rpc_xprt *xprt = req->rq_xprt;
+
+	spin_lock(&xprt->queue_lock);
+	xprt_request_dequeue_transmit_locked(task);
+	spin_unlock(&xprt->queue_lock);
+}
+
 /**
  * xprt_prepare_transmit - reserve the transport before sending a request
  * @task: RPC task about to send a request
@@ -1077,13 +1143,9 @@ bool xprt_prepare_transmit(struct rpc_task *task)
 			task->tk_status = req->rq_reply_bytes_recvd;
 			goto out_unlock;
 		}
-		if ((task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT) &&
-		    !xprt_request_retransmit_after_disconnect(task)) {
-			xprt->ops->set_retrans_timeout(task);
-			rpc_sleep_on(&xprt->pending, task, xprt_timer);
+		if (!test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
 			goto out_unlock;
 	}
-	}
 	if (!xprt->ops->reserve_xprt(xprt, task)) {
 		task->tk_status = -EAGAIN;
 		goto out_unlock;
@@ -1116,11 +1178,11 @@ void xprt_transmit(struct rpc_task *task)
 
 	if (!req->rq_bytes_sent) {
 		if (xprt_request_data_received(task))
-			return;
+			goto out_dequeue;
 		/* Verify that our message lies in the RPCSEC_GSS window */
 		if (rpcauth_xmit_need_reencode(task)) {
 			task->tk_status = -EBADMSG;
-			return;
+			goto out_dequeue;
 		}
 	}
 
@@ -1135,7 +1197,6 @@ void xprt_transmit(struct rpc_task *task)
 	xprt_inject_disconnect(xprt);
 
 	dprintk("RPC: %5u xmit complete\n", task->tk_pid);
-	clear_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
 	task->tk_flags |= RPC_TASK_SENT;
 	spin_lock_bh(&xprt->transport_lock);
 
@@ -1147,6 +1208,8 @@ void xprt_transmit(struct rpc_task *task)
 	spin_unlock_bh(&xprt->transport_lock);
 
 	req->rq_connect_cookie = connect_cookie;
+out_dequeue:
+	xprt_request_dequeue_transmit(task);
 }
 
 static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task)
@@ -1420,9 +1483,11 @@ xprt_request_dequeue_all(struct rpc_task *task, struct rpc_rqst *req)
 {
 	struct rpc_xprt *xprt = req->rq_xprt;
 
-	if (test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) ||
+	if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate) ||
+	    test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) ||
 	    xprt_is_pinned_rqst(req)) {
 		spin_lock(&xprt->queue_lock);
+		xprt_request_dequeue_transmit_locked(task);
 		xprt_request_dequeue_receive_locked(task);
 		while (xprt_is_pinned_rqst(req)) {
 			set_bit(RPC_TASK_MSG_PIN_WAIT, &task->tk_runstate);
@@ -1493,6 +1558,7 @@ static void xprt_init(struct rpc_xprt *xprt, struct net *net)
 
 	INIT_LIST_HEAD(&xprt->free);
 	INIT_LIST_HEAD(&xprt->recv_queue);
+	INIT_LIST_HEAD(&xprt->xmit_queue);
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 	spin_lock_init(&xprt->bc_pa_lock);
 	INIT_LIST_HEAD(&xprt->bc_pa_list);