[PATCH v3 net-next 12/15] ip6mr: Remove RTNL in ip6mr_rules_init() and ip6mr_net_init().

[Kuniyuki Iwashima <kuniyu@google.com>]

When ip6mr_free_table() is called from ip6mr_rules_init() or
ip6mr_net_init(), the netns is not yet published.

Thus, no device should have been registered, and
mroute_clean_tables() will not call mif6_delete(), so
unregister_netdevice_many() is unnecessary.

unregister_netdevice_many() does nothing if the list is empty,
but it requires RTNL due to the unconditional ASSERT_RTNL()
at the entry of unregister_netdevice_many_notify().

Let's remove unnecessary RTNL and ASSERT_RTNL() and instead
add WARN_ON_ONCE() in ip6mr_free_table().

Note that we use a local list for the new WARN_ON_ONCE() because
dev_kill_list passed from ip6mr_rules_exit_rtnl() may have some
devices when other ops->init() fails after ipmr durnig setup_net().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/ipv6/ip6mr.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 2220a2049781..e5a1d2c48b1b 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -263,10 +263,7 @@ static int __net_init ip6mr_rules_init(struct net *net)
 	return 0;
 
 err2:
-	rtnl_lock();
 	ip6mr_free_table(mrt, &dev_kill_list);
-	unregister_netdevice_many(&dev_kill_list);
-	rtnl_unlock();
 err1:
 	fib_rules_unregister(ops);
 	return err;
@@ -277,7 +274,6 @@ static void __net_exit ip6mr_rules_exit_rtnl(struct net *net,
 {
 	struct mr_table *mrt, *next;
 
-	ASSERT_RTNL();
 	list_for_each_entry_safe(mrt, next, &net->ipv6.mr6_tables, list) {
 		list_del(&mrt->list);
 		ip6mr_free_table(mrt, dev_kill_list);
@@ -343,7 +339,6 @@ static int __net_init ip6mr_rules_init(struct net *net)
 static void __net_exit ip6mr_rules_exit_rtnl(struct net *net,
 					     struct list_head *dev_kill_list)
 {
-	ASSERT_RTNL();
 	ip6mr_free_table(net->ipv6.mrt6, dev_kill_list);
 
 	net->ipv6.mrt6 = NULL;
@@ -414,15 +409,19 @@ static void ip6mr_free_table(struct mr_table *mrt,
 			     struct list_head *dev_kill_list)
 {
 	struct net *net = read_pnet(&mrt->net);
+	LIST_HEAD(ip6mr_dev_kill_list);
 
 	WARN_ON_ONCE(!mr_can_free_table(net));
 
 	timer_shutdown_sync(&mrt->ipmr_expire_timer);
 	mroute_clean_tables(mrt, MRT6_FLUSH_MIFS | MRT6_FLUSH_MIFS_STATIC |
 			    MRT6_FLUSH_MFC | MRT6_FLUSH_MFC_STATIC,
-			    dev_kill_list);
+			    &ip6mr_dev_kill_list);
 	rhltable_destroy(&mrt->mfc_hash);
 	kfree(mrt);
+
+	WARN_ON_ONCE(!net_initialized(net) && !list_empty(&ip6mr_dev_kill_list));
+	list_splice(&ip6mr_dev_kill_list, dev_kill_list);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -1364,10 +1363,7 @@ static int __net_init ip6mr_net_init(struct net *net)
 proc_cache_fail:
 	remove_proc_entry("ip6_mr_vif", net->proc_net);
 proc_vif_fail:
-	rtnl_lock();
 	ip6mr_rules_exit_rtnl(net, &dev_kill_list);
-	unregister_netdevice_many(&dev_kill_list);
-	rtnl_unlock();
 #endif
 ip6mr_rules_fail:
 	ip6mr_notifier_exit(net);
-- 
2.53.0.1213.gd9a14994de-goog