fs: dlm: relax sending to allow receiving

This patch drops additionally the sock_mutex when there is a sending
message burst. Since we have acknowledge handling we free sending
buffers only when we receive an ack back, but if we are stuck in
send_to_sock() looping because dlm sends a lot of messages and we never
leave the loop the sending buffer fill up very quickly. We can't receive
during this iteration because the sock_mutex is held. This patch will
unlock the sock_mutex so it should be possible to receive messages when
a burst of sending messages happens. This will allow to free up memory
because acks which are already received can be processed.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -1418,7 +1418,10 @@ static void send_to_sock(struct connection *con)
 	const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
 	struct writequeue_entry *e;
 	int len, offset, ret;
-	int count = 0;
+	int count;
+
+again:
+	count = 0;
 
 	mutex_lock(&con->sock_mutex);
 	if (con->sock == NULL)
@@ -1453,14 +1456,16 @@ static void send_to_sock(struct connection *con)
 		} else if (ret < 0)
 			goto out;
 
+		spin_lock(&con->writequeue_lock);
+		writequeue_entry_complete(e, ret);
+
 		/* Don't starve people filling buffers */
 		if (++count >= MAX_SEND_MSG_COUNT) {
+			spin_unlock(&con->writequeue_lock);
+			mutex_unlock(&con->sock_mutex);
 			cond_resched();
-			count = 0;
+			goto again;
 		}
-
-		spin_lock(&con->writequeue_lock);
-		writequeue_entry_complete(e, ret);
 	}
 	spin_unlock(&con->writequeue_lock);