[PATCH v1 net-next 5/5] ipv4: fib: Convert fib_net_exit_batch() to ->exit_rtnl().

[Kuniyuki Iwashima <kuniyu@google.com>]

Currently, IPv4 routes are flushed in ->exit_batch() after
all devices are unregistered.

Unlike IPv6, IPv4 routes are not added from the fast path,
so we can flush routes before default_device_exit_batch().

Let's call ip_fib_net_exit() from ->exit_rtnl() to save
one RTNL locking dance.

ip_fib_net_exit() must use list_del_rcu() for fib_table
for the fast path on dying dev.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/ipv4/fib_frontend.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index d147471d1d8e..c7d1f31650d7 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1607,7 +1607,7 @@ static void ip_fib_net_exit(struct net *net)
 		struct fib_table *tb;
 
 		hlist_for_each_entry_safe(tb, tmp, head, tb_hlist) {
-			hlist_del(&tb->tb_hlist);
+			hlist_del_rcu(&tb->tb_hlist);
 			fib_table_flush(net, tb, true);
 			fib_free_table(tb);
 		}
@@ -1663,29 +1663,24 @@ static void __net_exit fib_net_pre_exit(struct net *net)
 	nl_fib_lookup_exit(net);
 }
 
-static void __net_exit fib_net_exit_batch(struct list_head *net_list)
+static void __net_exit fib_net_exit_rtnl(struct net *net,
+					 struct list_head *dev_kill_list)
 {
-	struct net *net;
-
-	rtnl_lock();
-	list_for_each_entry(net, net_list, exit_list) {
-		__rtnl_net_lock(net);
-		ip_fib_net_exit(net);
-		__rtnl_net_unlock(net);
-	}
-	rtnl_unlock();
+	ip_fib_net_exit(net);
+}
 
-	list_for_each_entry(net, net_list, exit_list) {
-		kfree(net->ipv4.fib_table_hash);
-		fib4_notifier_exit(net);
-		fib4_semantics_exit(net);
-	}
+static void __net_exit fib_net_exit(struct net *net)
+{
+	kfree(net->ipv4.fib_table_hash);
+	fib4_notifier_exit(net);
+	fib4_semantics_exit(net);
 }
 
 static struct pernet_operations fib_net_ops = {
 	.init = fib_net_init,
 	.pre_exit = fib_net_pre_exit,
-	.exit_batch = fib_net_exit_batch,
+	.exit_rtnl = fib_net_exit_rtnl,
+	.exit = fib_net_exit,
 };
 
 static const struct rtnl_msg_handler fib_rtnl_msg_handlers[] __initconst = {
-- 
2.54.0.1136.gdb2ca164c4-goog