net: introduce upper device lists and remove dev->master

Jiri Pirko says:

====================
This is a V6 of a repost of my previous patchset:
"[patch net-next v2 00/15] net: introduce upper device lists and remove dev->master" from Aug 14

The discussion around
"[net-next] bonding: don't allow the master to become its slave"
forced me to think about upper<->lower device connections.

This patchset adds a possibility to record upper device linkage.
All upper<->lower devices are converted to use this mechanism right after.
That leads to dev->master removal because this info becomes redundant since
"master links" have the same value.

After all changes, there is no longer possible to do things as:
"bond->someotherdevice->samebond"

Also I think that drivers like cxgb3, qlcnic, qeth would benefit by this
in future by being able to get more appropriate info about l3 addresses.

v5->v6:
- netdev_has_upper_dev() - added statement to comment that this is looking at
  the immediate upper devices only.
- renamed "RTNL semaphore" -> "RTNL lock" in all comments
- renamed __netdev_has_upper_dev() to __netdev_search_upper_dev() to emhasize
  the difference to netdev_has_upper_dev()

v4->v5:
- fixed missed typo in drivers/infiniband/hw/nes/nes_cm.c

v3->v4:
- comments in __netdev_upper_dev_link() squashed into one line
- kfree_rcu used instead of call_rcu in netdev_upper_dev_unlink()

v2->v3:
- removed recursion in __netdev_has_upper_dev()
- refreshed bits to be applicable on current net-next

v1->v2:
- s/unique/master/ better naming + stays closer to the past
- fixed vlan err goto
- original patch 15 (WARN_ON change) is squashed into the first patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 8 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c5031a45e185..0209ac328e8a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -858,8 +858,7 @@ struct netdev_fcoe_hbainfo {
  *	flow_id is a flow ID to be passed to rps_may_expire_flow() later.
  *	Return the filter ID on success, or a negative error code.
  *
- *	Slave management functions (for bridge, bonding, etc). User should
- *	call netdev_set_master() to set dev->master properly.
+ *	Slave management functions (for bridge, bonding, etc).
  * int (*ndo_add_slave)(struct net_device *dev, struct net_device *slave_dev);
  *	Called to make another netdev an underling.
  *
@@ -1170,9 +1169,7 @@ struct net_device {
 						 * avoid dirtying this cache line.
 						 */
 
-	struct net_device	*master; /* Pointer to master device of a group,
-					  * which this device is member of.
-					  */
+	struct list_head	upper_dev_list; /* List of upper devices */
 
 	/* Interface address info used in eth_type_trans() */
 	unsigned char		*dev_addr;	/* hw address, (before bcast
@@ -2636,9 +2633,18 @@ extern int		netdev_max_backlog;
 extern int		netdev_tstamp_prequeue;
 extern int		weight_p;
 extern int		bpf_jit_enable;
-extern int		netdev_set_master(struct net_device *dev, struct net_device *master);
-extern int netdev_set_bond_master(struct net_device *dev,
-				  struct net_device *master);
+
+extern bool netdev_has_upper_dev(struct net_device *dev,
+				 struct net_device *upper_dev);
+extern bool netdev_has_any_upper_dev(struct net_device *dev);
+extern struct net_device *netdev_master_upper_dev_get(struct net_device *dev);
+extern struct net_device *netdev_master_upper_dev_get_rcu(struct net_device *dev);
+extern int netdev_upper_dev_link(struct net_device *dev,
+				 struct net_device *upper_dev);
+extern int netdev_master_upper_dev_link(struct net_device *dev,
+					struct net_device *upper_dev);
+extern void netdev_upper_dev_unlink(struct net_device *dev,
+				    struct net_device *upper_dev);
 extern int skb_checksum_help(struct sk_buff *skb);
 extern struct sk_buff *skb_gso_segment(struct sk_buff *skb,
 	netdev_features_t features);