tipc: add reference counter to bearer

As a need to support the crypto asynchronous operations in the later
commits, apart from the current RCU mechanism for bearer pointer, we
add a 'refcnt' to the bearer object as well.

So, a bearer can be hold via 'tipc_bearer_hold()' without being freed
even though the bearer or interface can be disabled in the meanwhile.
If that happens, the bearer will be released then when the crypto
operation is completed and 'tipc_bearer_put()' is called.

Acked-by: Ying Xue <ying.xue@windreiver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 1 deletions

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 0214aa1c4427..6e15b9b1f1ef 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -315,6 +315,7 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 	b->net_plane = bearer_id + 'A';
 	b->priority = prio;
 	test_and_set_bit_lock(0, &b->up);
+	refcount_set(&b->refcnt, 1);
 
 	res = tipc_disc_create(net, b, &b->bcast_addr, &skb);
 	if (res) {
@@ -351,6 +352,17 @@ static int tipc_reset_bearer(struct net *net, struct tipc_bearer *b)
 	return 0;
 }
 
+bool tipc_bearer_hold(struct tipc_bearer *b)
+{
+	return (b && refcount_inc_not_zero(&b->refcnt));
+}
+
+void tipc_bearer_put(struct tipc_bearer *b)
+{
+	if (b && refcount_dec_and_test(&b->refcnt))
+		kfree_rcu(b, rcu);
+}
+
 /**
  * bearer_disable
  *
@@ -369,7 +381,7 @@ static void bearer_disable(struct net *net, struct tipc_bearer *b)
 	if (b->disc)
 		tipc_disc_delete(b->disc);
 	RCU_INIT_POINTER(tn->bearer_list[bearer_id], NULL);
-	kfree_rcu(b, rcu);
+	tipc_bearer_put(b);
 	tipc_mon_delete(net, bearer_id);
 }