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>

1 files changed, 7 insertions, 15 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c50679f0a6b6..05e638b8ea25 100644
--- 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