[DLM] Use workqueues for dlm lowcomms

This patch converts the DLM TCP lowcomms to use workqueues rather than using its
own daemon functions. Simultaneously removing a lot of code and making it more
scalable on multi-processor machines.
Signed-Off-By: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/dlm/lowcomms-sctp.c

@@ -72,6 +72,8 @@ struct nodeinfo {
 	struct list_head	writequeue; /* outgoing writequeue_entries */
 	spinlock_t		writequeue_lock;
 	int			nodeid;
+	struct work_struct      swork; /* Send workqueue */
+	struct work_struct      lwork; /* Locking workqueue */
 };
 
 static DEFINE_IDR(nodeinfo_idr);
@@ -96,6 +98,7 @@ struct connection {
 	atomic_t		waiting_requests;
 	struct cbuf		cb;
 	int                     eagain_flag;
+	struct work_struct      work; /* Send workqueue */
 };
 
 /* An entry waiting to be sent */
@@ -137,19 +140,23 @@ static void cbuf_eat(struct cbuf *cb, int n)
 static LIST_HEAD(write_nodes);
 static DEFINE_SPINLOCK(write_nodes_lock);
 
+
 /* Maximum number of incoming messages to process before
  * doing a schedule()
  */
 #define MAX_RX_MSG_COUNT 25
 
-/* Manage daemons */
-static struct task_struct *recv_task;
-static struct task_struct *send_task;
-static DECLARE_WAIT_QUEUE_HEAD(lowcomms_recv_wait);
+/* Work queues */
+static struct workqueue_struct *recv_workqueue;
+static struct workqueue_struct *send_workqueue;
+static struct workqueue_struct *lock_workqueue;
 
 /* The SCTP connection */
 static struct connection sctp_con;
 
+static void process_send_sockets(struct work_struct *work);
+static void process_recv_sockets(struct work_struct *work);
+static void process_lock_request(struct work_struct *work);
 
 static int nodeid_to_addr(int nodeid, struct sockaddr *retaddr)
 {
@@ -222,6 +229,8 @@ static struct nodeinfo *nodeid2nodeinfo(int nodeid, gfp_t alloc)
 	spin_lock_init(&ni->lock);
 	INIT_LIST_HEAD(&ni->writequeue);
 	spin_lock_init(&ni->writequeue_lock);
+	INIT_WORK(&ni->lwork, process_lock_request);
+	INIT_WORK(&ni->swork, process_send_sockets);
 	ni->nodeid = nodeid;
 
 	if (nodeid > max_nodeid)
@@ -249,11 +258,8 @@ static struct nodeinfo *assoc2nodeinfo(sctp_assoc_t assoc)
 /* Data or notification available on socket */
 static void lowcomms_data_ready(struct sock *sk, int count_unused)
 {
-	atomic_inc(&sctp_con.waiting_requests);
 	if (test_and_set_bit(CF_READ_PENDING, &sctp_con.flags))
-		return;
-
-	wake_up_interruptible(&lowcomms_recv_wait);
+		queue_work(recv_workqueue, &sctp_con.work);
 }
 
 
@@ -361,10 +367,10 @@ static void init_failed(void)
 				spin_lock_bh(&write_nodes_lock);
 				list_add_tail(&ni->write_list, &write_nodes);
 				spin_unlock_bh(&write_nodes_lock);
+				queue_work(send_workqueue, &ni->swork);
 			}
 		}
 	}
-	wake_up_process(send_task);
 }
 
 /* Something happened to an association */
@@ -446,8 +452,8 @@ static void process_sctp_notification(struct msghdr *msg, char *buf)
 				spin_lock_bh(&write_nodes_lock);
 				list_add_tail(&ni->write_list, &write_nodes);
 				spin_unlock_bh(&write_nodes_lock);
+				queue_work(send_workqueue, &ni->swork);
 			}
-			wake_up_process(send_task);
 		}
 		break;
 
@@ -580,8 +586,8 @@ static int receive_from_sock(void)
 				spin_lock_bh(&write_nodes_lock);
 				list_add_tail(&ni->write_list, &write_nodes);
 				spin_unlock_bh(&write_nodes_lock);
+				queue_work(send_workqueue, &ni->swork);
 			}
-			wake_up_process(send_task);
 		}
 	}
 
@@ -590,6 +596,7 @@ static int receive_from_sock(void)
 		return 0;
 
 	cbuf_add(&sctp_con.cb, ret);
+	// PJC: TODO: Add to node's workqueue....can we ??
 	ret = dlm_process_incoming_buffer(cpu_to_le32(sinfo->sinfo_ppid),
 					  page_address(sctp_con.rx_page),
 					  sctp_con.cb.base, sctp_con.cb.len,
@@ -820,7 +827,8 @@ void dlm_lowcomms_commit_buffer(void *arg)
 		spin_lock_bh(&write_nodes_lock);
 		list_add_tail(&ni->write_list, &write_nodes);
 		spin_unlock_bh(&write_nodes_lock);
-		wake_up_process(send_task);
+
+		queue_work(send_workqueue, &ni->swork);
 	}
 	return;
 
@@ -1088,33 +1096,12 @@ int dlm_lowcomms_close(int nodeid)
 	return 0;
 }
 
-static int write_list_empty(void)
-{
-	int status;
-
-	spin_lock_bh(&write_nodes_lock);
-	status = list_empty(&write_nodes);
-	spin_unlock_bh(&write_nodes_lock);
-
-	return status;
-}
-
-static int dlm_recvd(void *data)
+// PJC: The work queue function for receiving.
+static void process_recv_sockets(struct work_struct *work)
 {
-	DECLARE_WAITQUEUE(wait, current);
-
-	while (!kthread_should_stop()) {
-		int count = 0;
-
-		set_current_state(TASK_INTERRUPTIBLE);
-		add_wait_queue(&lowcomms_recv_wait, &wait);
-		if (!test_bit(CF_READ_PENDING, &sctp_con.flags))
-			schedule();
-		remove_wait_queue(&lowcomms_recv_wait, &wait);
-		set_current_state(TASK_RUNNING);
-
 	if (test_and_clear_bit(CF_READ_PENDING, &sctp_con.flags)) {
 		int ret;
+		int count = 0;
 
 		do {
 			ret = receive_from_sock();
@@ -1127,62 +1114,57 @@ static int dlm_recvd(void *data)
 		} while (!kthread_should_stop() && ret >=0);
 	}
 	cond_resched();
-	}
-
-	return 0;
 }
 
-static int dlm_sendd(void *data)
+// PJC: the work queue function for sending
+static void process_send_sockets(struct work_struct *work)
 {
-	DECLARE_WAITQUEUE(wait, current);
-
-	add_wait_queue(sctp_con.sock->sk->sk_sleep, &wait);
-
-	while (!kthread_should_stop()) {
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (write_list_empty())
-			schedule();
-		set_current_state(TASK_RUNNING);
-
 	if (sctp_con.eagain_flag) {
 		sctp_con.eagain_flag = 0;
 		refill_write_queue();
 	}
 	process_output_queue();
-	}
-
-	remove_wait_queue(sctp_con.sock->sk->sk_sleep, &wait);
+}
 
-	return 0;
+// PJC: Process lock requests from a particular node.
+// TODO: can we optimise this out on UP ??
+static void process_lock_request(struct work_struct *work)
+{
 }
 
 static void daemons_stop(void)
 {
-	kthread_stop(recv_task);
-	kthread_stop(send_task);
+	destroy_workqueue(recv_workqueue);
+	destroy_workqueue(send_workqueue);
+	destroy_workqueue(lock_workqueue);
 }
 
 static int daemons_start(void)
 {
-	struct task_struct *p;
 	int error;
+	recv_workqueue = create_workqueue("dlm_recv");
+	error = IS_ERR(recv_workqueue);
+	if (error) {
+		log_print("can't start dlm_recv %d", error);
+		return error;
+	}
 
-	p = kthread_run(dlm_recvd, NULL, "dlm_recvd");
-	error = IS_ERR(p);
+	send_workqueue = create_singlethread_workqueue("dlm_send");
+	error = IS_ERR(send_workqueue);
 	if (error) {
-		log_print("can't start dlm_recvd %d", error);
+		log_print("can't start dlm_send %d", error);
+		destroy_workqueue(recv_workqueue);
 		return error;
 	}
-	recv_task = p;
 
-	p = kthread_run(dlm_sendd, NULL, "dlm_sendd");
-	error = IS_ERR(p);
+	lock_workqueue = create_workqueue("dlm_rlock");
+	error = IS_ERR(lock_workqueue);
 	if (error) {
-		log_print("can't start dlm_sendd %d", error);
-		kthread_stop(recv_task);
+		log_print("can't start dlm_rlock %d", error);
+		destroy_workqueue(send_workqueue);
+		destroy_workqueue(recv_workqueue);
 		return error;
 	}
-	send_task = p;
 
 	return 0;
 }
@@ -1194,6 +1176,8 @@ int dlm_lowcomms_start(void)
 {
 	int error;
 
+	INIT_WORK(&sctp_con.work, process_recv_sockets);
+
 	error = init_sock();
 	if (error)
 		goto fail_sock;
@@ -1224,4 +1208,3 @@ void dlm_lowcomms_stop(void)
 	for (i = 0; i < dlm_local_count; i++)
 		kfree(dlm_local_addr[i]);
 }
-