Merge branch 'net-convert-exit_batch_rtnl-to-exit_rtnl'

Kuniyuki Iwashima says:

====================
net: Convert ->exit_batch_rtnl() to ->exit_rtnl().

While converting nexthop to per-netns RTNL, there are two blockers
to using rtnl_net_dereference(), flush_all_nexthops() and
__unregister_nexthop_notifier(), both of which are called from
->exit_batch_rtnl().

Instead of spreading __rtnl_net_lock() over each ->exit_batch_rtnl(),
we should convert all ->exit_batch_rtnl() to per-net ->exit_rtnl() and
run it under __rtnl_net_lock() because all ->exit_batch_rtnl() functions
do not have anything to factor out for batching.

Patch 1 & 2 factorise the undo mechanism against ->init() into a single
function, and Patch 3 adds ->exit_batch_rtnl().

Patch 4 ~ 13 convert all ->exit_batch_rtnl() users.

Patch 14 removes ->exit_batch_rtnl().

Later, we can convert pfcp and ppp to use ->exit_rtnl().

v1: https://lore.kernel.org/all/20250410022004.8668-1-kuniyu@amazon.com/
====================

Link: https://patch.msgid.link/20250411205258.63164-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 95 insertions, 86 deletions

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index b0dfdf791ece..0a2b24af4028 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -163,16 +163,45 @@ static void ops_pre_exit_list(const struct pernet_operations *ops,
 	}
 }
 
+static void ops_exit_rtnl_list(const struct list_head *ops_list,
+			       const struct pernet_operations *ops,
+			       struct list_head *net_exit_list)
+{
+	const struct pernet_operations *saved_ops = ops;
+	LIST_HEAD(dev_kill_list);
+	struct net *net;
+
+	rtnl_lock();
+
+	list_for_each_entry(net, net_exit_list, exit_list) {
+		__rtnl_net_lock(net);
+
+		ops = saved_ops;
+		list_for_each_entry_continue_reverse(ops, ops_list, list) {
+			if (ops->exit_rtnl)
+				ops->exit_rtnl(net, &dev_kill_list);
+		}
+
+		__rtnl_net_unlock(net);
+	}
+
+	unregister_netdevice_many(&dev_kill_list);
+
+	rtnl_unlock();
+}
+
 static void ops_exit_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
-	struct net *net;
 	if (ops->exit) {
+		struct net *net;
+
 		list_for_each_entry(net, net_exit_list, exit_list) {
 			ops->exit(net);
 			cond_resched();
 		}
 	}
+
 	if (ops->exit_batch)
 		ops->exit_batch(net_exit_list);
 }
@@ -188,6 +217,54 @@ static void ops_free_list(const struct pernet_operations *ops,
 	}
 }
 
+static void ops_undo_list(const struct list_head *ops_list,
+			  const struct pernet_operations *ops,
+			  struct list_head *net_exit_list,
+			  bool expedite_rcu, bool hold_rtnl)
+{
+	const struct pernet_operations *saved_ops;
+
+	if (!ops)
+		ops = list_entry(ops_list, typeof(*ops), list);
+
+	saved_ops = ops;
+
+	list_for_each_entry_continue_reverse(ops, ops_list, list)
+		ops_pre_exit_list(ops, net_exit_list);
+
+	/* Another CPU might be rcu-iterating the list, wait for it.
+	 * This needs to be before calling the exit() notifiers, so the
+	 * rcu_barrier() after ops_undo_list() isn't sufficient alone.
+	 * Also the pre_exit() and exit() methods need this barrier.
+	 */
+	if (expedite_rcu)
+		synchronize_rcu_expedited();
+	else
+		synchronize_rcu();
+
+	if (hold_rtnl)
+		ops_exit_rtnl_list(ops_list, saved_ops, net_exit_list);
+
+	ops = saved_ops;
+	list_for_each_entry_continue_reverse(ops, ops_list, list)
+		ops_exit_list(ops, net_exit_list);
+
+	ops = saved_ops;
+	list_for_each_entry_continue_reverse(ops, ops_list, list)
+		ops_free_list(ops, net_exit_list);
+}
+
+static void ops_undo_single(struct pernet_operations *ops,
+			    struct list_head *net_exit_list)
+{
+	bool hold_rtnl = !!ops->exit_rtnl;
+	LIST_HEAD(ops_list);
+
+	list_add(&ops->list, &ops_list);
+	ops_undo_list(&ops_list, NULL, net_exit_list, false, hold_rtnl);
+	list_del(&ops->list);
+}
+
 /* should be called with nsid_lock held */
 static int alloc_netid(struct net *net, struct net *peer, int reqid)
 {
@@ -351,9 +428,8 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_
 static __net_init int setup_net(struct net *net)
 {
 	/* Must be called with pernet_ops_rwsem held */
-	const struct pernet_operations *ops, *saved_ops;
+	const struct pernet_operations *ops;
 	LIST_HEAD(net_exit_list);
-	LIST_HEAD(dev_kill_list);
 	int error = 0;
 
 	preempt_disable();
@@ -376,29 +452,7 @@ out_undo:
 	 * for the pernet modules whose init functions did not fail.
 	 */
 	list_add(&net->exit_list, &net_exit_list);
-	saved_ops = ops;
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-		ops_pre_exit_list(ops, &net_exit_list);
-
-	synchronize_rcu();
-
-	ops = saved_ops;
-	rtnl_lock();
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
-		if (ops->exit_batch_rtnl)
-			ops->exit_batch_rtnl(&net_exit_list, &dev_kill_list);
-	}
-	unregister_netdevice_many(&dev_kill_list);
-	rtnl_unlock();
-
-	ops = saved_ops;
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-		ops_exit_list(ops, &net_exit_list);
-
-	ops = saved_ops;
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-		ops_free_list(ops, &net_exit_list);
-
+	ops_undo_list(&pernet_list, ops, &net_exit_list, false, true);
 	rcu_barrier();
 	goto out;
 }
@@ -594,11 +648,9 @@ struct task_struct *cleanup_net_task;
 
 static void cleanup_net(struct work_struct *work)
 {
-	const struct pernet_operations *ops;
-	struct net *net, *tmp, *last;
 	struct llist_node *net_kill_list;
+	struct net *net, *tmp, *last;
 	LIST_HEAD(net_exit_list);
-	LIST_HEAD(dev_kill_list);
 
 	cleanup_net_task = current;
 
@@ -629,33 +681,7 @@ static void cleanup_net(struct work_struct *work)
 		list_add_tail(&net->exit_list, &net_exit_list);
 	}
 
-	/* Run all of the network namespace pre_exit methods */
-	list_for_each_entry_reverse(ops, &pernet_list, list)
-		ops_pre_exit_list(ops, &net_exit_list);
-
-	/*
-	 * Another CPU might be rcu-iterating the list, wait for it.
-	 * This needs to be before calling the exit() notifiers, so
-	 * the rcu_barrier() below isn't sufficient alone.
-	 * Also the pre_exit() and exit() methods need this barrier.
-	 */
-	synchronize_rcu_expedited();
-
-	rtnl_lock();
-	list_for_each_entry_reverse(ops, &pernet_list, list) {
-		if (ops->exit_batch_rtnl)
-			ops->exit_batch_rtnl(&net_exit_list, &dev_kill_list);
-	}
-	unregister_netdevice_many(&dev_kill_list);
-	rtnl_unlock();
-
-	/* Run all of the network namespace exit methods */
-	list_for_each_entry_reverse(ops, &pernet_list, list)
-		ops_exit_list(ops, &net_exit_list);
-
-	/* Free the net generic variables */
-	list_for_each_entry_reverse(ops, &pernet_list, list)
-		ops_free_list(ops, &net_exit_list);
+	ops_undo_list(&pernet_list, NULL, &net_exit_list, true, true);
 
 	up_read(&pernet_ops_rwsem);
 
@@ -1239,31 +1265,13 @@ void __init net_ns_init(void)
 	rtnl_register_many(net_ns_rtnl_msg_handlers);
 }
 
-static void free_exit_list(struct pernet_operations *ops, struct list_head *net_exit_list)
-{
-	ops_pre_exit_list(ops, net_exit_list);
-	synchronize_rcu();
-
-	if (ops->exit_batch_rtnl) {
-		LIST_HEAD(dev_kill_list);
-
-		rtnl_lock();
-		ops->exit_batch_rtnl(net_exit_list, &dev_kill_list);
-		unregister_netdevice_many(&dev_kill_list);
-		rtnl_unlock();
-	}
-	ops_exit_list(ops, net_exit_list);
-
-	ops_free_list(ops, net_exit_list);
-}
-
 #ifdef CONFIG_NET_NS
 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
+	LIST_HEAD(net_exit_list);
 	struct net *net;
 	int error;
-	LIST_HEAD(net_exit_list);
 
 	list_add_tail(&ops->list, list);
 	if (ops->init || ops->id) {
@@ -1282,21 +1290,21 @@ static int __register_pernet_operations(struct list_head *list,
 out_undo:
 	/* If I have an error cleanup all namespaces I initialized */
 	list_del(&ops->list);
-	free_exit_list(ops, &net_exit_list);
+	ops_undo_single(ops, &net_exit_list);
 	return error;
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-	struct net *net;
 	LIST_HEAD(net_exit_list);
+	struct net *net;
 
-	list_del(&ops->list);
 	/* See comment in __register_pernet_operations() */
 	for_each_net(net)
 		list_add_tail(&net->exit_list, &net_exit_list);
 
-	free_exit_list(ops, &net_exit_list);
+	list_del(&ops->list);
+	ops_undo_single(ops, &net_exit_list);
 }
 
 #else
@@ -1304,22 +1312,23 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
-	if (!init_net_initialized) {
-		list_add_tail(&ops->list, list);
+	list_add_tail(&ops->list, list);
+
+	if (!init_net_initialized)
 		return 0;
-	}
 
 	return ops_init(ops, &init_net);
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-	if (!init_net_initialized) {
-		list_del(&ops->list);
-	} else {
+	list_del(&ops->list);
+
+	if (init_net_initialized) {
 		LIST_HEAD(net_exit_list);
+
 		list_add(&init_net.exit_list, &net_exit_list);
-		free_exit_list(ops, &net_exit_list);
+		ops_undo_single(ops, &net_exit_list);
 	}
 }