At this moment after .newlink and .changelink are switched
to __register_netdevice(), there must not be calls of
register_netdevice() with lock attached.

Signed-off-by: Kirill Tkhai <tkhai@ya.ru>
---
 net/core/dev.c |   17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 63ece39c9286..e6809a80644e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10847,25 +10847,14 @@ int register_netdevice(struct net_device *dev)
 	struct nd_lock *nd_lock;
 	int err;
 
-	/* XXX: This "if" is to start one by one convertation
-	 * to use __register_netdevice() in devices, that
-	 * want to attach nd_lock themself (e.g., having newlink).
-	 * After all of them are converted, we remove this.
-	 */
-	if (rcu_access_pointer(dev->nd_lock))
-		return __register_netdevice(dev);
+	if (WARN_ON(rcu_access_pointer(dev->nd_lock)))
+		return -EINVAL;
 
 	nd_lock = alloc_nd_lock();
 	if (!nd_lock)
 		return -ENOMEM;
 
-	/* This may be called from netdevice notifier, which is not converted
-	 * yet. The context is unknown: either some nd_lock is locked or not.
-	 * Sometimes here is nested mutex and sometimes is not. We use trylock
-	 * to silence lockdep assert about that.
-	 * It will be replaced by mutex_lock(), see next patches.
-	 */
-	BUG_ON(!mutex_trylock(&nd_lock->mutex));
+	mutex_lock(&nd_lock->mutex);
 	attach_nd_lock(dev, nd_lock);
 	err = __register_netdevice(dev);
 	if (err)