ipv4: add __unregister_nexthop_notifier()

unregister_nexthop_notifier() assumes the caller does not hold rtnl.

We need in the following patch to use it from a context
already holding rtnl.

Add __unregister_nexthop_notifier().

unregister_nexthop_notifier() becomes a wrapper.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://lore.kernel.org/r/20240206144313.2050392-9-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/nexthop.h

@@ -218,6 +218,7 @@ struct nh_notifier_info {
 
 int register_nexthop_notifier(struct net *net, struct notifier_block *nb,
 			      struct netlink_ext_ack *extack);
+int __unregister_nexthop_notifier(struct net *net, struct notifier_block *nb);
 int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb);
 void nexthop_set_hw_flags(struct net *net, u32 id, bool offload, bool trap);
 void nexthop_bucket_set_hw_flags(struct net *net, u32 id, u16 bucket_index,

net/ipv4/nexthop.c

@@ -3631,17 +3631,24 @@ int register_nexthop_notifier(struct net *net, struct notifier_block *nb,
 }
 EXPORT_SYMBOL(register_nexthop_notifier);
 
-int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb)
+int __unregister_nexthop_notifier(struct net *net, struct notifier_block *nb)
 {
 	int err;
 
-	rtnl_lock();
 	err = blocking_notifier_chain_unregister(&net->nexthop.notifier_chain,
 						 nb);
-	if (err)
-		goto unlock;
-	nexthops_dump(net, nb, NEXTHOP_EVENT_DEL, NULL);
-unlock:
+	if (!err)
+		nexthops_dump(net, nb, NEXTHOP_EVENT_DEL, NULL);
+	return err;
+}
+EXPORT_SYMBOL(__unregister_nexthop_notifier);
+
+int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb)
+{
+	int err;
+
+	rtnl_lock();
+	err = __unregister_nexthop_notifier(net, nb);
 	rtnl_unlock();
 	return err;
 }