bonding: rebuild the lock use for bond_alb_monitor()

The bond_alb_monitor use bond lock to protect the bond slave list,
it is no effect here, we need to use RTNL or RCU to replace bond lock,
the bond_alb_monitor will called 10 times one second, RTNL may loss
performance here, so I replace bond lock with RCU to protect the
bond slave list, also the RTNL is preserved, the logic of the monitor
did not changed.
Suggested-by: Nikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: Jay Vosburgh <fubar@us.ibm.com>
Suggested-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_alb.c

@@ -815,7 +815,7 @@ static void rlb_rebalance(struct bonding *bond)
 	for (; hash_index != RLB_NULL_INDEX;
 	     hash_index = client_info->used_next) {
 		client_info = &(bond_info->rx_hashtbl[hash_index]);
-		assigned_slave = rlb_next_rx_slave(bond);
+		assigned_slave = __rlb_next_rx_slave(bond);
 		if (assigned_slave && (client_info->slave != assigned_slave)) {
 			client_info->slave = assigned_slave;
 			client_info->ntt = 1;
@@ -1494,14 +1494,14 @@ void bond_alb_monitor(struct work_struct *work)
 	struct list_head *iter;
 	struct slave *slave;
 
-	read_lock(&bond->lock);
-
 	if (!bond_has_slaves(bond)) {
 		bond_info->tx_rebalance_counter = 0;
 		bond_info->lp_counter = 0;
 		goto re_arm;
 	}
 
+	rcu_read_lock();
+
 	bond_info->tx_rebalance_counter++;
 	bond_info->lp_counter++;
 
@@ -1514,7 +1514,7 @@ void bond_alb_monitor(struct work_struct *work)
 		 */
 		read_lock(&bond->curr_slave_lock);
 
-		bond_for_each_slave(bond, slave, iter)
+		bond_for_each_slave_rcu(bond, slave, iter)
 			alb_send_learning_packets(slave, slave->dev->dev_addr);
 
 		read_unlock(&bond->curr_slave_lock);
@@ -1527,7 +1527,7 @@ void bond_alb_monitor(struct work_struct *work)
 
 		read_lock(&bond->curr_slave_lock);
 
-		bond_for_each_slave(bond, slave, iter) {
+		bond_for_each_slave_rcu(bond, slave, iter) {
 			tlb_clear_slave(bond, slave, 1);
 			if (slave == bond->curr_active_slave) {
 				SLAVE_TLB_INFO(slave).load =
@@ -1551,11 +1551,9 @@ void bond_alb_monitor(struct work_struct *work)
 			 * dev_set_promiscuity requires rtnl and
 			 * nothing else.  Avoid race with bond_close.
 			 */
-			read_unlock(&bond->lock);
-			if (!rtnl_trylock()) {
-				read_lock(&bond->lock);
+			rcu_read_unlock();
+			if (!rtnl_trylock())
 				goto re_arm;
-			}
 
 			bond_info->rlb_promisc_timeout_counter = 0;
 
@@ -1567,7 +1565,7 @@ void bond_alb_monitor(struct work_struct *work)
 			bond_info->primary_is_promisc = 0;
 
 			rtnl_unlock();
-			read_lock(&bond->lock);
+			rcu_read_lock();
 		}
 
 		if (bond_info->rlb_rebalance) {
@@ -1589,11 +1587,9 @@ void bond_alb_monitor(struct work_struct *work)
 			}
 		}
 	}
-
+	rcu_read_unlock();
 re_arm:
 	queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
-
-	read_unlock(&bond->lock);
 }
 
 /* assumption: called before the slave is attached to the bond