bonding: simplify and fix peer notification

This patch aims to remove a use of the bond->lock for mutual exclusion
which will later allow easier migration to RCU of the users of this
functionality. We use RTNL as a synchronizing mechanism since it's
always held when send_peer_notif is set, and when it is decremented from
the notifier function. We can also drop some locking, and fix the
leakage of the send_peer_notif counter.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c50679f..05e638b 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -828,7 +828,6 @@ static bool bond_should_notify_peers(struct bonding *bond)
            test_bit(__LINK_STATE_LINKWATCH_PENDING, &slave->dev->state))
                return false;
 
-       bond->send_peer_notif--;
        return true;
 }
 
@@ -2259,12 +2258,8 @@ re_arm:
        read_unlock(&bond->lock);
 
        if (should_notify_peers) {
-               if (!rtnl_trylock()) {
-                       read_lock(&bond->lock);
-                       bond->send_peer_notif++;
-                       read_unlock(&bond->lock);
+               if (!rtnl_trylock())
                        return;
-               }
                call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev);
                rtnl_unlock();
        }
@@ -2876,12 +2871,8 @@ re_arm:
        read_unlock(&bond->lock);
 
        if (should_notify_peers) {
-               if (!rtnl_trylock()) {
-                       read_lock(&bond->lock);
-                       bond->send_peer_notif++;
-                       read_unlock(&bond->lock);
+               if (!rtnl_trylock())
                        return;
-               }
                call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev);
                rtnl_unlock();
        }
@@ -2916,6 +2907,10 @@ static int bond_master_netdev_event(unsigned long event,
        case NETDEV_REGISTER:
                bond_create_proc_entry(event_bond);
                break;
+       case NETDEV_NOTIFY_PEERS:
+               if (event_bond->send_peer_notif)
+                       event_bond->send_peer_notif--;
+               break;
        default:
                break;
        }
@@ -3213,11 +3208,8 @@ static int bond_close(struct net_device *bond_dev)
 {
        struct bonding *bond = netdev_priv(bond_dev);
 
-       write_lock_bh(&bond->lock);
-       bond->send_peer_notif = 0;
-       write_unlock_bh(&bond->lock);
-
        bond_work_cancel_all(bond);
+       bond->send_peer_notif = 0;
        if (bond_is_lb(bond)) {
                /* Must be called only after all
                 * slaves have been released