bonding: remove bond read lock for bond_alb_monitor()

The bond slave list may change when the monitor is running, the slave list is no longer
protected by bond->lock, only protected by rtnl lock(), so we have 3 ways to modify it:
1.add bond_master_upper_dev_link() and bond_upper_dev_unlink() in bond->lock, but it is unsafe
to call call_netdevice_notifiers() in write lock.
2.remove unused bond->lock for monitor function, only use the existing rtnl lock().
3.use rcu_read_lock() to protect it, of course, it will transform bond_for_each_slave to
bond_for_each_slave_rcu() and performance is better, but in slow path, it is ignored.
so I remove the bond->lock and move the rtnl lock to protect the whole monitor function.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 02872405d35dc4a53d13473b31d1b517d22610d0..5d79f5e529e05c3d8655b10142e89afe60b654b8 100644 (file)
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1495,11 +1495,13 @@ void bond_alb_monitor(struct work_struct *work)
        struct list_head *iter;
        struct slave *slave;
 
-       read_lock(&bond->lock);
+       if (!rtnl_trylock())
+               goto re_arm;
 
        if (!bond_has_slaves(bond)) {
                bond_info->tx_rebalance_counter = 0;
                bond_info->lp_counter = 0;
+               rtnl_unlock();
                goto re_arm;
        }
 
@@ -1548,16 +1550,6 @@ void bond_alb_monitor(struct work_struct *work)
                if (bond_info->primary_is_promisc &&
                    (++bond_info->rlb_promisc_timeout_counter >= RLB_PROMISC_TIMEOUT)) {
 
-                       /*
-                        * dev_set_promiscuity requires rtnl and
-                        * nothing else.  Avoid race with bond_close.
-                        */
-                       read_unlock(&bond->lock);
-                       if (!rtnl_trylock()) {
-                               read_lock(&bond->lock);
-                               goto re_arm;
-                       }
-
                        bond_info->rlb_promisc_timeout_counter = 0;
 
                        /* If the primary was set to promiscuous mode
@@ -1566,9 +1558,6 @@ void bond_alb_monitor(struct work_struct *work)
                         */
                        dev_set_promiscuity(bond->curr_active_slave->dev, -1);
                        bond_info->primary_is_promisc = 0;
-
-                       rtnl_unlock();
-                       read_lock(&bond->lock);
                }
 
                if (bond_info->rlb_rebalance) {
@@ -1591,10 +1580,9 @@ void bond_alb_monitor(struct work_struct *work)
                }
        }
 
+       rtnl_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