bonding: convert curr_slave_lock to a spinlock and rename it

curr_slave_lock is now a misleading name, a much better name is
mode_lock as it'll be used for each mode's purposes and it's no longer
necessary to use a rwlock, a simple spinlock is enough.

Suggested-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_3ad.c

@@ -2057,7 +2057,7 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
 	struct port *port;
 	bool should_notify_rtnl = BOND_SLAVE_NOTIFY_LATER;
 
-	read_lock(&bond->curr_slave_lock);
+	spin_lock_bh(&bond->mode_lock);
 	rcu_read_lock();
 
 	/* check if there are any slaves */
@@ -2120,7 +2120,7 @@ re_arm:
 		}
 	}
 	rcu_read_unlock();
-	read_unlock(&bond->curr_slave_lock);
+	spin_unlock_bh(&bond->mode_lock);
 
 	if (should_notify_rtnl && rtnl_trylock()) {
 		bond_slave_state_notify(bond);

drivers/net/bonding/bond_main.c

@@ -1679,9 +1679,9 @@ static int __bond_release_one(struct net_device *bond_dev,
 		/* Sync against bond_3ad_rx_indication and
 		 * bond_3ad_state_machine_handler
 		 */
-		write_lock_bh(&bond->curr_slave_lock);
+		spin_lock_bh(&bond->mode_lock);
 		bond_3ad_unbind_slave(slave);
-		write_unlock_bh(&bond->curr_slave_lock);
+		spin_unlock_bh(&bond->mode_lock);
 	}
 
 	netdev_info(bond_dev, "Releasing %s interface %s\n",
@@ -3850,8 +3850,7 @@ void bond_setup(struct net_device *bond_dev)
 {
 	struct bonding *bond = netdev_priv(bond_dev);
 
-	/* initialize rwlocks */
-	rwlock_init(&bond->curr_slave_lock);
+	spin_lock_init(&bond->mode_lock);
 	bond->params = bonding_defaults;
 
 	/* Initialize pointers */

drivers/net/bonding/bonding.h

@@ -195,7 +195,7 @@ struct bonding {
 	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
 	int     (*recv_probe)(const struct sk_buff *, struct bonding *,
 			      struct slave *);
-	rwlock_t curr_slave_lock;
+	spinlock_t mode_lock;
 	u8	 send_peer_notif;
 	u8       igmp_retrans;
 #ifdef CONFIG_PROC_FS