drbd: debugfs: Add in_flight_summary

* Add details about pending meta data operations to in_flight_summary.

* Report number of requests waiting for activity log transactions.

* timing details of peer_requests to in_flight_summary.

* FLUSH details
  DRBD devides the incoming request stream into "epochs",
  in which peers are allowed to re-order writes independendly.

  These epochs are separated by P_BARRIER on the replication link.
  Such barrier packets, depending on configuration, may cause
  the receiving side to drain the lower level device request queues
  and call blkdev_issue_flush().

  This is known to be an other major source of latency in DRBD.

  Track timing details of calls to blkdev_issue_flush(),
  and add them to in_flight_summary.

* data socket stats
  To be able to diagnose bottlenecks and root causes of "slow" IO on DRBD,
  it is useful to see network buffer stats along with the timing details of
  requests, peer requests, and meta data IO.

* pending bitmap IO timing details to in_flight_summary.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 19 insertions, 14 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 01de57ec0110..9712bcc8e069 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2982,24 +2982,29 @@ void drbd_free_ldev(struct drbd_backing_dev *ldev)
 	kfree(ldev);
 }
 
-void drbd_free_sock(struct drbd_connection *connection)
+static void drbd_free_one_sock(struct drbd_socket *ds)
 {
-	if (connection->data.socket) {
-		mutex_lock(&connection->data.mutex);
-		kernel_sock_shutdown(connection->data.socket, SHUT_RDWR);
-		sock_release(connection->data.socket);
-		connection->data.socket = NULL;
-		mutex_unlock(&connection->data.mutex);
-	}
-	if (connection->meta.socket) {
-		mutex_lock(&connection->meta.mutex);
-		kernel_sock_shutdown(connection->meta.socket, SHUT_RDWR);
-		sock_release(connection->meta.socket);
-		connection->meta.socket = NULL;
-		mutex_unlock(&connection->meta.mutex);
+	struct socket *s;
+	mutex_lock(&ds->mutex);
+	s = ds->socket;
+	ds->socket = NULL;
+	mutex_unlock(&ds->mutex);
+	if (s) {
+		/* so debugfs does not need to mutex_lock() */
+		synchronize_rcu();
+		kernel_sock_shutdown(s, SHUT_RDWR);
+		sock_release(s);
 	}
 }
 
+void drbd_free_sock(struct drbd_connection *connection)
+{
+	if (connection->data.socket)
+		drbd_free_one_sock(&connection->data);
+	if (connection->meta.socket)
+		drbd_free_one_sock(&connection->meta);
+}
+
 /* meta data management */
 
 void conn_md_sync(struct drbd_connection *connection)