ceph: fix multiple mds session shutdown

The use of a completion when waiting for session shutdown during umount is
inappropriate, given the complexity of the condition.  For multiple MDS's,
this resulted in the umount thread spinning, often preventing the session
close message from being processed in some cases.

Switch to a waitqueue and defined a condition helper.  This cleans things
up nicely.

Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 35 insertions, 33 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a75ddbf..397a47b 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2208,7 +2208,7 @@ static void handle_session(struct ceph_mds_session *session,
 			pr_info("mds%d reconnect denied\n", session->s_mds);
 		remove_session_caps(session);
 		wake = 1; /* for good measure */
-		complete_all(&mdsc->session_close_waiters);
+		wake_up_all(&mdsc->session_close_wq);
 		kick_requests(mdsc, mds);
 		break;
 
@@ -2876,7 +2876,7 @@ int ceph_mdsc_init(struct ceph_mds_client *mdsc, struct ceph_client *client)
 		return -ENOMEM;
 
 	init_completion(&mdsc->safe_umount_waiters);
-	init_completion(&mdsc->session_close_waiters);
+	init_waitqueue_head(&mdsc->session_close_wq);
 	INIT_LIST_HEAD(&mdsc->waiting_for_map);
 	mdsc->sessions = NULL;
 	mdsc->max_sessions = 0;
@@ -3021,6 +3021,23 @@ void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
 	wait_event(mdsc->cap_flushing_wq, check_cap_flush(mdsc, want_flush));
 }
 
+/*
+ * true if all sessions are closed, or we force unmount
+ */
+bool done_closing_sessions(struct ceph_mds_client *mdsc)
+{
+	int i, n = 0;
+
+	if (mdsc->client->mount_state == CEPH_MOUNT_SHUTDOWN)
+		return true;
+
+	mutex_lock(&mdsc->mutex);
+	for (i = 0; i < mdsc->max_sessions; i++)
+		if (mdsc->sessions[i])
+			n++;
+	mutex_unlock(&mdsc->mutex);
+	return n == 0;
+}
 
 /*
  * called after sb is ro.
@@ -3029,45 +3046,32 @@ void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
 {
 	struct ceph_mds_session *session;
 	int i;
-	int n;
 	struct ceph_client *client = mdsc->client;
-	unsigned long started, timeout = client->mount_args->mount_timeout * HZ;
+	unsigned long timeout = client->mount_args->mount_timeout * HZ;
 
 	dout("close_sessions\n");
 
-	mutex_lock(&mdsc->mutex);
-
 	/* close sessions */
-	started = jiffies;
-	while (time_before(jiffies, started + timeout)) {
-		dout("closing sessions\n");
-		n = 0;
-		for (i = 0; i < mdsc->max_sessions; i++) {
-			session = __ceph_lookup_mds_session(mdsc, i);
-			if (!session)
-				continue;
-			mutex_unlock(&mdsc->mutex);
-			mutex_lock(&session->s_mutex);
-			__close_session(mdsc, session);
-			mutex_unlock(&session->s_mutex);
-			ceph_put_mds_session(session);
-			mutex_lock(&mdsc->mutex);
-			n++;
-		}
-		if (n == 0)
-			break;
-
-		if (client->mount_state == CEPH_MOUNT_SHUTDOWN)
-			break;
-
-		dout("waiting for sessions to close\n");
+	mutex_lock(&mdsc->mutex);
+	for (i = 0; i < mdsc->max_sessions; i++) {
+		session = __ceph_lookup_mds_session(mdsc, i);
+		if (!session)
+			continue;
 		mutex_unlock(&mdsc->mutex);
-		wait_for_completion_timeout(&mdsc->session_close_waiters,
-					    timeout);
+		mutex_lock(&session->s_mutex);
+		__close_session(mdsc, session);
+		mutex_unlock(&session->s_mutex);
+		ceph_put_mds_session(session);
 		mutex_lock(&mdsc->mutex);
 	}
+	mutex_unlock(&mdsc->mutex);
+
+	dout("waiting for sessions to close\n");
+	wait_event_timeout(mdsc->session_close_wq, done_closing_sessions(mdsc),
+			   timeout);
 
 	/* tear down remaining sessions */
+	mutex_lock(&mdsc->mutex);
 	for (i = 0; i < mdsc->max_sessions; i++) {
 		if (mdsc->sessions[i]) {
 			session = get_session(mdsc->sessions[i]);
@@ -3080,9 +3084,7 @@ void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
 			mutex_lock(&mdsc->mutex);
 		}
 	}
-
 	WARN_ON(!list_empty(&mdsc->cap_delay_list));
-
 	mutex_unlock(&mdsc->mutex);
 
 	ceph_cleanup_empty_realms(mdsc);