libceph: factor out ceph_con_get_out_msg()

Move the logic of grabbing the next message from the queue into its own
function.  Like ceph_con_in_msg_alloc(), this is protocol independent.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/messenger.c

@@ -1304,6 +1304,8 @@ static void prepare_write_message_footer(struct ceph_connection *con)
 	con->out_msg_done = true;
 }
 
+static void ceph_con_get_out_msg(struct ceph_connection *con);
+
 /*
  * Prepare headers for the next outgoing message.
  */
@@ -1325,26 +1327,8 @@ static void prepare_write_message(struct ceph_connection *con)
 			&con->out_temp_ack);
 	}
 
-	BUG_ON(list_empty(&con->out_queue));
-	m = list_first_entry(&con->out_queue, struct ceph_msg, list_head);
-	con->out_msg = m;
-	BUG_ON(m->con != con);
-
-	/* put message on sent list */
-	ceph_msg_get(m);
-	list_move_tail(&m->list_head, &con->out_sent);
-
-	/*
-	 * only assign outgoing seq # if we haven't sent this message
-	 * yet.  if it is requeued, resend with it's original seq.
-	 */
-	if (m->needs_out_seq) {
-		m->hdr.seq = cpu_to_le64(++con->out_seq);
-		m->needs_out_seq = false;
-
-		if (con->ops->reencode_message)
-			con->ops->reencode_message(m);
-	}
+	ceph_con_get_out_msg(con);
+	m = con->out_msg;
 
 	dout("prepare_write_message %p seq %lld type %d len %d+%d+%zd\n",
 	     m, con->out_seq, le16_to_cpu(m->hdr.type),
@@ -3118,6 +3102,8 @@ static void clear_standby(struct ceph_connection *con)
 
 /*
  * Queue up an outgoing message on the given connection.
+ *
+ * Consumes a ref on @msg.
  */
 void ceph_con_send(struct ceph_connection *con, struct ceph_msg *msg)
 {
@@ -3503,6 +3489,39 @@ static int ceph_con_in_msg_alloc(struct ceph_connection *con,
 	return ret;
 }
 
+static void ceph_con_get_out_msg(struct ceph_connection *con)
+{
+	struct ceph_msg *msg;
+
+	BUG_ON(list_empty(&con->out_queue));
+	msg = list_first_entry(&con->out_queue, struct ceph_msg, list_head);
+	WARN_ON(msg->con != con);
+
+	/*
+	 * Put the message on "sent" list using a ref from ceph_con_send().
+	 * It is put when the message is acked or revoked.
+	 */
+	list_move_tail(&msg->list_head, &con->out_sent);
+
+	/*
+	 * Only assign outgoing seq # if we haven't sent this message
+	 * yet.  If it is requeued, resend with it's original seq.
+	 */
+	if (msg->needs_out_seq) {
+		msg->hdr.seq = cpu_to_le64(++con->out_seq);
+		msg->needs_out_seq = false;
+
+		if (con->ops->reencode_message)
+			con->ops->reencode_message(msg);
+	}
+
+	/*
+	 * Get a ref for out_msg.  It is put when we are done sending the
+	 * message or in case of a fault.
+	 */
+	WARN_ON(con->out_msg);
+	con->out_msg = ceph_msg_get(msg);
+}
 
 /*
  * Free a generically kmalloc'd message.