net: bridge: switchdev: fix shim definition for br_switchdev_mdb_notify

br_switchdev_mdb_notify() is conditionally compiled only when
CONFIG_NET_SWITCHDEV=y and CONFIG_BRIDGE_IGMP_SNOOPING=y. It is called
from br_mdb.c, which is conditionally compiled only when
CONFIG_BRIDGE_IGMP_SNOOPING=y.

The shim definition of br_switchdev_mdb_notify() is therefore needed for
the case where CONFIG_NET_SWITCHDEV=n, however we mistakenly put it
there for the case where CONFIG_BRIDGE_IGMP_SNOOPING=n. This results in
build failures when CONFIG_BRIDGE_IGMP_SNOOPING=y and
CONFIG_NET_SWITCHDEV=n.

To fix this, put the shim definition right next to
br_switchdev_fdb_notify(), which is properly guarded by NET_SWITCHDEV=n.
Since this is called only from br_mdb.c, we need not take any extra
safety precautions, when NET_SWITCHDEV=n and BRIDGE_IGMP_SNOOPING=n,
this shim definition will be absent but nobody will be needing it.

Fixes: 9776457c ("net: bridge: mdb: move all switchdev logic to br_switchdev.c")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20211029223606.3450523-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/bridge/br_private.h

@@ -956,11 +956,6 @@ int br_multicast_toggle_vlan_snooping(struct net_bridge *br, bool on,
 				      struct netlink_ext_ack *extack);
 bool br_multicast_toggle_global_vlan(struct net_bridge_vlan *vlan, bool on);
 
-void br_switchdev_mdb_notify(struct net_device *dev,
-			     struct net_bridge_mdb_entry *mp,
-			     struct net_bridge_port_group *pg,
-			     int type);
-
 int br_rports_fill_info(struct sk_buff *skb,
 			const struct net_bridge_mcast *brmctx);
 int br_multicast_dump_querier_state(struct sk_buff *skb,
@@ -1396,13 +1391,6 @@ static inline bool br_multicast_toggle_global_vlan(struct net_bridge_vlan *vlan,
 	return false;
 }
 
-static inline void br_switchdev_mdb_notify(struct net_device *dev,
-					   struct net_bridge_mdb_entry *mp,
-					   struct net_bridge_port_group *pg,
-					   int type)
-{
-}
-
 static inline bool
 br_multicast_ctx_options_equal(const struct net_bridge_mcast *brmctx1,
 			       const struct net_bridge_mcast *brmctx2)
@@ -1983,6 +1971,10 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p,
 			       struct netlink_ext_ack *extack);
 void br_switchdev_fdb_notify(struct net_bridge *br,
 			     const struct net_bridge_fdb_entry *fdb, int type);
+void br_switchdev_mdb_notify(struct net_device *dev,
+			     struct net_bridge_mdb_entry *mp,
+			     struct net_bridge_port_group *pg,
+			     int type);
 int br_switchdev_port_vlan_add(struct net_device *dev, u16 vid, u16 flags,
 			       struct netlink_ext_ack *extack);
 int br_switchdev_port_vlan_del(struct net_device *dev, u16 vid);
@@ -2069,6 +2061,13 @@ br_switchdev_fdb_notify(struct net_bridge *br,
 {
 }
 
+static inline void br_switchdev_mdb_notify(struct net_device *dev,
+					   struct net_bridge_mdb_entry *mp,
+					   struct net_bridge_port_group *pg,
+					   int type)
+{
+}
+
 static inline void br_switchdev_frame_unmark(struct sk_buff *skb)
 {
 }