lowcomms.c

		addr = kmalloc(sizeof(*addr), GFP_KERNEL);
		if (!addr)
			break;
		memcpy(addr, &sas, sizeof(*addr));
		dlm_local_addr[dlm_local_count++] = addr;
	}
}

/* Bind to an IP address. SCTP allows multiple address so it can do
   multi-homing */
static int add_sctp_bind_addr(struct connection *sctp_con,
			      struct sockaddr_storage *addr,
			      int addr_len, int num)
{
	int result = 0;

	if (num == 1)
		result = kernel_bind(sctp_con->sock,
				     (struct sockaddr *) addr,
				     addr_len);
	else
		result = kernel_setsockopt(sctp_con->sock, SOL_SCTP,
					   SCTP_SOCKOPT_BINDX_ADD,
					   (char *)addr, addr_len);

	if (result < 0)
		log_print("Can't bind to port %d addr number %d",
			  dlm_config.ci_tcp_port, num);

	return result;
}

/* Initialise SCTP socket and bind to all interfaces */
static int sctp_listen_for_all(void)
{
	struct socket *sock = NULL;
	struct sockaddr_storage localaddr;
	struct sctp_event_subscribe subscribe;
	int result = -EINVAL, num = 1, i, addr_len;
	struct connection *con = nodeid2con(0, GFP_KERNEL);
	int bufsize = NEEDED_RMEM;

	if (!con)
		return -ENOMEM;

	log_print("Using SCTP for communications");

	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_SEQPACKET,
				  IPPROTO_SCTP, &sock);
	if (result < 0) {
		log_print("Can't create comms socket, check SCTP is loaded");
		goto out;
	}

	/* Listen for events */
	memset(&subscribe, 0, sizeof(subscribe));
	subscribe.sctp_data_io_event = 1;
	subscribe.sctp_association_event = 1;
	subscribe.sctp_send_failure_event = 1;
	subscribe.sctp_shutdown_event = 1;
	subscribe.sctp_partial_delivery_event = 1;

	result = kernel_setsockopt(sock, SOL_SOCKET, SO_RCVBUF,
				 (char *)&bufsize, sizeof(bufsize));
	if (result)
		log_print("Error increasing buffer space on socket %d", result);

	result = kernel_setsockopt(sock, SOL_SCTP, SCTP_EVENTS,
				   (char *)&subscribe, sizeof(subscribe));
	if (result < 0) {
		log_print("Failed to set SCTP_EVENTS on socket: result=%d",
			  result);
		goto create_delsock;
	}

	/* Init con struct */
	sock->sk->sk_user_data = con;
	con->sock = sock;
	con->sock->sk->sk_data_ready = lowcomms_data_ready;
	con->rx_action = receive_from_sock;
	con->connect_action = sctp_init_assoc;

	/* Bind to all interfaces. */
	for (i = 0; i < dlm_local_count; i++) {
		memcpy(&localaddr, dlm_local_addr[i], sizeof(localaddr));
		make_sockaddr(&localaddr, dlm_config.ci_tcp_port, &addr_len);

		result = add_sctp_bind_addr(con, &localaddr, addr_len, num);
		if (result)
			goto create_delsock;
		++num;
	}

	result = sock->ops->listen(sock, 5);
	if (result < 0) {
		log_print("Can't set socket listening");
		goto create_delsock;
	}

	return 0;

create_delsock:
	sock_release(sock);
	con->sock = NULL;
out:
	return result;
}

static int tcp_listen_for_all(void)
{
	struct socket *sock = NULL;
	struct connection *con = nodeid2con(0, GFP_KERNEL);
	int result = -EINVAL;

	if (!con)
		return -ENOMEM;

	/* We don't support multi-homed hosts */
	if (dlm_local_addr[1] != NULL) {
		log_print("TCP protocol can't handle multi-homed hosts, "
			  "try SCTP");
		return -EINVAL;
	}

	log_print("Using TCP for communications");

	set_bit(CF_IS_OTHERCON, &con->flags);

	sock = tcp_create_listen_sock(con, dlm_local_addr[0]);
	if (sock) {
		add_sock(sock, con);
		result = 0;
	}
	else {
		result = -EADDRINUSE;
	}

	return result;
}



static struct writequeue_entry *new_writequeue_entry(struct connection *con,
						     gfp_t allocation)
{
	struct writequeue_entry *entry;

	entry = kmalloc(sizeof(struct writequeue_entry), allocation);
	if (!entry)
		return NULL;

	entry->page = alloc_page(allocation);
	if (!entry->page) {
		kfree(entry);
		return NULL;
	}

	entry->offset = 0;
	entry->len = 0;
	entry->end = 0;
	entry->users = 0;
	entry->con = con;

	return entry;
}

void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
{
	struct connection *con;
	struct writequeue_entry *e;
	int offset = 0;
	int users = 0;

	con = nodeid2con(nodeid, allocation);
	if (!con)
		return NULL;

	spin_lock(&con->writequeue_lock);
	e = list_entry(con->writequeue.prev, struct writequeue_entry, list);
	if ((&e->list == &con->writequeue) ||
	    (PAGE_CACHE_SIZE - e->end < len)) {
		e = NULL;
	} else {
		offset = e->end;
		e->end += len;
		users = e->users++;
	}
	spin_unlock(&con->writequeue_lock);

	if (e) {
	got_one:
		if (users == 0)
			kmap(e->page);
		*ppc = page_address(e->page) + offset;
		return e;
	}

	e = new_writequeue_entry(con, allocation);
	if (e) {
		spin_lock(&con->writequeue_lock);
		offset = e->end;
		e->end += len;
		users = e->users++;
		list_add_tail(&e->list, &con->writequeue);
		spin_unlock(&con->writequeue_lock);
		goto got_one;
	}
	return NULL;
}

void dlm_lowcomms_commit_buffer(void *mh)
{
	struct writequeue_entry *e = (struct writequeue_entry *)mh;
	struct connection *con = e->con;
	int users;

	spin_lock(&con->writequeue_lock);
	users = --e->users;
	if (users)
		goto out;
	e->len = e->end - e->offset;
	kunmap(e->page);
	spin_unlock(&con->writequeue_lock);

	if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags)) {
		queue_work(send_workqueue, &con->swork);
	}
	return;

out:
	spin_unlock(&con->writequeue_lock);
	return;
}

/* Send a message */
static void send_to_sock(struct connection *con)
{
	int ret = 0;
	ssize_t(*sendpage) (struct socket *, struct page *, int, size_t, int);
	const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
	struct writequeue_entry *e;
	int len, offset;

	mutex_lock(&con->sock_mutex);
	if (con->sock == NULL)
		goto out_connect;

	sendpage = con->sock->ops->sendpage;

	spin_lock(&con->writequeue_lock);
	for (;;) {
		e = list_entry(con->writequeue.next, struct writequeue_entry,
			       list);
		if ((struct list_head *) e == &con->writequeue)
			break;

		len = e->len;
		offset = e->offset;
		BUG_ON(len == 0 && e->users == 0);
		spin_unlock(&con->writequeue_lock);
		kmap(e->page);

		ret = 0;
		if (len) {
			ret = sendpage(con->sock, e->page, offset, len,
				       msg_flags);
			if (ret == -EAGAIN || ret == 0)
				goto out;
			if (ret <= 0)
				goto send_error;
		} else {
			/* Don't starve people filling buffers */
			cond_resched();
		}

		spin_lock(&con->writequeue_lock);
		e->offset += ret;
		e->len -= ret;

		if (e->len == 0 && e->users == 0) {
			list_del(&e->list);
			kunmap(e->page);
			free_entry(e);
			continue;
		}
	}
	spin_unlock(&con->writequeue_lock);
out:
	mutex_unlock(&con->sock_mutex);
	return;

send_error:
	mutex_unlock(&con->sock_mutex);
	close_connection(con, false);
	lowcomms_connect_sock(con);
	return;

out_connect:
	mutex_unlock(&con->sock_mutex);
	if (!test_bit(CF_INIT_PENDING, &con->flags))
		lowcomms_connect_sock(con);
	return;
}

static void clean_one_writequeue(struct connection *con)
{
	struct list_head *list;
	struct list_head *temp;

	spin_lock(&con->writequeue_lock);
	list_for_each_safe(list, temp, &con->writequeue) {
		struct writequeue_entry *e =
			list_entry(list, struct writequeue_entry, list);
		list_del(&e->list);
		free_entry(e);
	}
	spin_unlock(&con->writequeue_lock);
}

/* Called from recovery when it knows that a node has
   left the cluster */
int dlm_lowcomms_close(int nodeid)
{
	struct connection *con;

	log_print("closing connection to node %d", nodeid);
	con = nodeid2con(nodeid, 0);
	if (con) {
		clean_one_writequeue(con);
		close_connection(con, true);
	}
	return 0;
}

/* Receive workqueue function */
static void process_recv_sockets(struct work_struct *work)
{
	struct connection *con = container_of(work, struct connection, rwork);
	int err;

	clear_bit(CF_READ_PENDING, &con->flags);
	do {
		err = con->rx_action(con);
	} while (!err);
}

/* Send workqueue function */
static void process_send_sockets(struct work_struct *work)
{
	struct connection *con = container_of(work, struct connection, swork);

	if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
		con->connect_action(con);
	}
	clear_bit(CF_WRITE_PENDING, &con->flags);
	send_to_sock(con);
}


/* Discard all entries on the write queues */
static void clean_writequeues(void)
{
	int nodeid;

	for (nodeid = 1; nodeid <= max_nodeid; nodeid++) {
		struct connection *con = __nodeid2con(nodeid, 0);

		if (con)
			clean_one_writequeue(con);
	}
}

static void work_stop(void)
{
	destroy_workqueue(recv_workqueue);
	destroy_workqueue(send_workqueue);
}

static int work_start(void)
{
	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;
	}

	send_workqueue = create_singlethread_workqueue("dlm_send");
	error = IS_ERR(send_workqueue);
	if (error) {
		log_print("can't start dlm_send %d", error);
		destroy_workqueue(recv_workqueue);
		return error;
	}

	return 0;
}

void dlm_lowcomms_stop(void)
{
	int i;
	struct connection *con;

	/* Set all the flags to prevent any
	   socket activity.
	*/
	down(&connections_lock);
	for (i = 0; i <= max_nodeid; i++) {
		con = __nodeid2con(i, 0);
		if (con) {
			con->flags |= 0xFF;
			if (con->sock)
				con->sock->sk->sk_user_data = NULL;
		}
	}
	up(&connections_lock);

	work_stop();

	down(&connections_lock);
	clean_writequeues();

	for (i = 0; i <= max_nodeid; i++) {
		con = __nodeid2con(i, 0);
		if (con) {
			close_connection(con, true);
			if (con->othercon)
				kmem_cache_free(con_cache, con->othercon);
			kmem_cache_free(con_cache, con);
		}
	}
	max_nodeid = 0;
	up(&connections_lock);
	kmem_cache_destroy(con_cache);
	idr_init(&connections_idr);
}

int dlm_lowcomms_start(void)
{
	int error = -EINVAL;
	struct connection *con;

	init_local();
	if (!dlm_local_count) {
		error = -ENOTCONN;
		log_print("no local IP address has been set");
		goto out;
	}

	error = -ENOMEM;
	con_cache = kmem_cache_create("dlm_conn", sizeof(struct connection),
				      __alignof__(struct connection), 0,
				      NULL);
	if (!con_cache)
		goto out;

	/* Set some sysctl minima */
	if (sysctl_rmem_max < NEEDED_RMEM)
		sysctl_rmem_max = NEEDED_RMEM;

	/* Start listening */
	if (dlm_config.ci_protocol == 0)
		error = tcp_listen_for_all();
	else
		error = sctp_listen_for_all();
	if (error)
		goto fail_unlisten;

	error = work_start();
	if (error)
		goto fail_unlisten;

	return 0;

fail_unlisten:
	con = nodeid2con(0,0);
	if (con) {
		close_connection(con, false);
		kmem_cache_free(con_cache, con);
	}
	kmem_cache_destroy(con_cache);

out:
	return error;
}