tipc: add option to suppress PUBLISH events for pre-existing publications

Currently, when a user is subscribing for binding table publications,
he will receive a PUBLISH event for all already existing matching items
in the binding table.

However, a group socket making a subscriptions doesn't need this initial
status update from the binding table, because it has already scanned it
during the join operation. Worse, the multiplicatory effect of issuing
mutual events for dozens or hundreds group members within a short time
frame put a heavy load on the topology server, with the end result that
scale out operations on a big group tend to take much longer than needed.

We now add a new filter option, TIPC_SUB_NO_STATUS, for topology server
subscriptions, so that this initial avalanche of events is suppressed.
This change, along with the previous commit, significantly improves the
range and speed of group scale out operations.

We keep the new option internal for the tipc driver, at least for now.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 4 deletions

diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
index 251065dfd8df..1052341a0ea9 100644
--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -286,7 +286,8 @@ static struct tipc_subscription *tipc_subscrp_create(struct net *net,
 }
 
 static void tipc_subscrp_subscribe(struct net *net, struct tipc_subscr *s,
-				   struct tipc_subscriber *subscriber, int swap)
+				   struct tipc_subscriber *subscriber, int swap,
+				   bool status)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_subscription *sub = NULL;
@@ -299,7 +300,7 @@ static void tipc_subscrp_subscribe(struct net *net, struct tipc_subscr *s,
 	spin_lock_bh(&subscriber->lock);
 	list_add(&sub->subscrp_list, &subscriber->subscrp_list);
 	sub->subscriber = subscriber;
-	tipc_nametbl_subscribe(sub);
+	tipc_nametbl_subscribe(sub, status);
 	tipc_subscrb_get(subscriber);
 	spin_unlock_bh(&subscriber->lock);
 
@@ -323,6 +324,7 @@ static void tipc_subscrb_rcv_cb(struct net *net, int conid,
 {
 	struct tipc_subscriber *subscriber = usr_data;
 	struct tipc_subscr *s = (struct tipc_subscr *)buf;
+	bool status;
 	int swap;
 
 	/* Determine subscriber's endianness */
@@ -334,8 +336,8 @@ static void tipc_subscrb_rcv_cb(struct net *net, int conid,
 		s->filter &= ~htohl(TIPC_SUB_CANCEL, swap);
 		return tipc_subscrp_cancel(s, subscriber);
 	}
-
-	tipc_subscrp_subscribe(net, s, subscriber, swap);
+	status = !(s->filter & htohl(TIPC_SUB_NO_STATUS, swap));
+	tipc_subscrp_subscribe(net, s, subscriber, swap, status);
 }
 
 /* Handle one request to establish a new subscriber */