Merge branch 'dev-hold-per-netns-rtnl-in-register-netdev'

Kuniyuki Iwashima says:

====================
dev: Hold per-netns RTNL in register_netdev().

Patch 1 adds rtnl_net_lock_killable() and Patch 2 uses it in
register_netdev() and converts it and unregister_netdev() to
per-netns RTNL.

With this and the netdev notifier series [0], ASSERT_RTNL_NET()
for NETDEV_REGISTER [1] wasn't fired on a simplest QEMU setup
like e1000 + x86_64_defconfig + CONFIG_DEBUG_NET_SMALL_RTNL.

[0]: https://lore.kernel.org/netdev/20250104063735.36945-1-kuniyu@amazon.com/

[1]:
---8<---
diff --git a/net/core/rtnl_net_debug.c b/net/core/rtnl_net_debug.c
index f406045cbd0e..c0c30929002e 100644
--- a/net/core/rtnl_net_debug.c
+++ b/net/core/rtnl_net_debug.c
@@ -21,7 +21,6 @@ static int rtnl_net_debug_event(struct notifier_block *nb,
 	case NETDEV_DOWN:
 	case NETDEV_REBOOT:
 	case NETDEV_CHANGE:
-	case NETDEV_REGISTER:
 	case NETDEV_UNREGISTER:
 	case NETDEV_CHANGEMTU:
 	case NETDEV_CHANGEADDR:
@@ -60,19 +59,10 @@ static int rtnl_net_debug_event(struct notifier_block *nb,
 		ASSERT_RTNL();
 		break;

-	/* Once an event fully supports RTNL_NET, move it here
-	 * and remove "if (0)" below.
-	 *
-	 * case NETDEV_XXX:
-	 *	ASSERT_RTNL_NET(net);
-	 *	break;
-	 */
-	}
-
-	/* Just to avoid unused-variable error for dev and net. */
-	if (0)
+	case NETDEV_REGISTER:
 		ASSERT_RTNL_NET(net);
+		break;
+	}

 	return NOTIFY_DONE;
 }
---8<---
====================

Link: https://patch.msgid.link/20250104082149.48493-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

3 files changed, 26 insertions, 5 deletions

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 3b9d132cbc9e..4bc2ee0b10b0 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -102,6 +102,7 @@ void __rtnl_net_unlock(struct net *net);
 void rtnl_net_lock(struct net *net);
 void rtnl_net_unlock(struct net *net);
 int rtnl_net_trylock(struct net *net);
+int rtnl_net_lock_killable(struct net *net);
 int rtnl_net_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b);
 
 bool rtnl_net_is_locked(struct net *net);
@@ -138,6 +139,11 @@ static inline int rtnl_net_trylock(struct net *net)
 	return rtnl_trylock();
 }
 
+static inline int rtnl_net_lock_killable(struct net *net)
+{
+	return rtnl_lock_killable();
+}
+
 static inline void ASSERT_RTNL_NET(struct net *net)
 {
 	ASSERT_RTNL();
diff --git a/net/core/dev.c b/net/core/dev.c
index e7223972b9aa..073f682a9653 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10731,12 +10731,16 @@ EXPORT_SYMBOL_GPL(init_dummy_netdev);
  */
 int register_netdev(struct net_device *dev)
 {
+	struct net *net = dev_net(dev);
 	int err;
 
-	if (rtnl_lock_killable())
+	if (rtnl_net_lock_killable(net))
 		return -EINTR;
+
 	err = register_netdevice(dev);
-	rtnl_unlock();
+
+	rtnl_net_unlock(net);
+
 	return err;
 }
 EXPORT_SYMBOL(register_netdev);
@@ -11606,9 +11610,11 @@ EXPORT_SYMBOL(unregister_netdevice_many);
  */
 void unregister_netdev(struct net_device *dev)
 {
-	rtnl_lock();
+	struct net *net = dev_net(dev);
+
+	rtnl_net_lock(net);
 	unregister_netdevice(dev);
-	rtnl_unlock();
+	rtnl_net_unlock(net);
 }
 EXPORT_SYMBOL(unregister_netdev);
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 6b745096809d..1f4d4b5570ab 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -84,7 +84,6 @@ int rtnl_lock_killable(void)
 {
 	return mutex_lock_killable(&rtnl_mutex);
 }
-EXPORT_SYMBOL(rtnl_lock_killable);
 
 static struct sk_buff *defer_kfree_skb_list;
 void rtnl_kfree_skbs(struct sk_buff *head, struct sk_buff *tail)
@@ -221,6 +220,16 @@ int rtnl_net_trylock(struct net *net)
 }
 EXPORT_SYMBOL(rtnl_net_trylock);
 
+int rtnl_net_lock_killable(struct net *net)
+{
+	int ret = rtnl_lock_killable();
+
+	if (!ret)
+		__rtnl_net_lock(net);
+
+	return ret;
+}
+
 static int rtnl_net_cmp_locks(const struct net *net_a, const struct net *net_b)
 {
 	if (net_eq(net_a, net_b))