net: remove type_check from dev_get_nest_level()

The idea for type_check in dev_get_nest_level() was to count the number
of nested devices of the same type (currently, only macvlan or vlan
devices).
This prevented the false positive lockdep warning on configurations such
as:

eth0 <--- macvlan0 <--- vlan0 <--- macvlan1

However, this doesn't prevent a warning on a configuration such as:

eth0 <--- macvlan0 <--- vlan0
eth1 <--- vlan1 <--- macvlan1

In this case, all the locks end up with a nesting subclass of 1, so
lockdep thinks that there is still a deadlock:

- in the first case we have (macvlan_netdev_addr_lock_key, 1) and then
  take (vlan_netdev_xmit_lock_key, 1)
- in the second case, we have (vlan_netdev_xmit_lock_key, 1) and then
  take (macvlan_netdev_addr_lock_key, 1)

By removing the linktype check in dev_get_nest_level() and always
incrementing the nesting depth, lockdep considers this configuration
valid.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 8 deletions

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 82a116b..8de138d 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -169,7 +169,7 @@ int register_vlan_dev(struct net_device *dev)
 	if (err < 0)
 		goto out_uninit_mvrp;
 
-	vlan->nest_level = dev_get_nest_level(real_dev, is_vlan_dev) + 1;
+	vlan->nest_level = dev_get_nest_level(real_dev) + 1;
 	err = register_netdevice(dev);
 	if (err < 0)
 		goto out_uninit_mvrp;
diff --git a/net/core/dev.c b/net/core/dev.c
index 4ce07dc..dd6ce59 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6045,8 +6045,7 @@ void *netdev_lower_dev_get_private(struct net_device *dev,
 EXPORT_SYMBOL(netdev_lower_dev_get_private);
 
 
-int dev_get_nest_level(struct net_device *dev,
-		       bool (*type_check)(const struct net_device *dev))
+int dev_get_nest_level(struct net_device *dev)
 {
 	struct net_device *lower = NULL;
 	struct list_head *iter;
@@ -6056,15 +6055,12 @@ int dev_get_nest_level(struct net_device *dev,
 	ASSERT_RTNL();
 
 	netdev_for_each_lower_dev(dev, lower, iter) {
-		nest = dev_get_nest_level(lower, type_check);
+		nest = dev_get_nest_level(lower);
 		if (max_nest < nest)
 			max_nest = nest;
 	}
 
-	if (type_check(dev))
-		max_nest++;
-
-	return max_nest;
+	return max_nest + 1;
 }
 EXPORT_SYMBOL(dev_get_nest_level);