tcp/dccp: get rid of inet_twsk_purge()

Prior patches in the series made sure tw_timer_handler()
can be fired after netns has been dismantled/freed.

We no longer have to scan a potentially big TCP ehash
table at netns dismantle.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_timewait_sock.h

@@ -110,8 +110,6 @@ static inline void inet_twsk_reschedule(struct inet_timewait_sock *tw, int timeo
 
 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw);
 
-void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family);
-
 static inline
 struct net *twsk_net(const struct inet_timewait_sock *twsk)
 {

net/dccp/ipv4.c

@@ -1030,15 +1030,9 @@ static void __net_exit dccp_v4_exit_net(struct net *net)
 	inet_ctl_sock_destroy(pn->v4_ctl_sk);
 }
 
-static void __net_exit dccp_v4_exit_batch(struct list_head *net_exit_list)
-{
-	inet_twsk_purge(&dccp_hashinfo, AF_INET);
-}
-
 static struct pernet_operations dccp_v4_ops = {
 	.init	= dccp_v4_init_net,
 	.exit	= dccp_v4_exit_net,
-	.exit_batch = dccp_v4_exit_batch,
 	.id	= &dccp_v4_pernet_id,
 	.size   = sizeof(struct dccp_v4_pernet),
 };

net/dccp/ipv6.c

@@ -1115,15 +1115,9 @@ static void __net_exit dccp_v6_exit_net(struct net *net)
 	inet_ctl_sock_destroy(pn->v6_ctl_sk);
 }
 
-static void __net_exit dccp_v6_exit_batch(struct list_head *net_exit_list)
-{
-	inet_twsk_purge(&dccp_hashinfo, AF_INET6);
-}
-
 static struct pernet_operations dccp_v6_ops = {
 	.init   = dccp_v6_init_net,
 	.exit   = dccp_v6_exit_net,
-	.exit_batch = dccp_v6_exit_batch,
 	.id	= &dccp_v6_pernet_id,
 	.size   = sizeof(struct dccp_v6_pernet),
 };

net/ipv4/inet_timewait_sock.c

@@ -255,50 +255,3 @@ void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
 	}
 }
 EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
-
-void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
-{
-	struct inet_timewait_sock *tw;
-	struct sock *sk;
-	struct hlist_nulls_node *node;
-	unsigned int slot;
-
-	for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
-		struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
-restart_rcu:
-		cond_resched();
-		rcu_read_lock();
-restart:
-		sk_nulls_for_each_rcu(sk, node, &head->chain) {
-			if (sk->sk_state != TCP_TIME_WAIT)
-				continue;
-			tw = inet_twsk(sk);
-			if ((tw->tw_family != family) ||
-				refcount_read(&twsk_net(tw)->ns.count))
-				continue;
-
-			if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
-				continue;
-
-			if (unlikely((tw->tw_family != family) ||
-				     refcount_read(&twsk_net(tw)->ns.count))) {
-				inet_twsk_put(tw);
-				goto restart;
-			}
-
-			rcu_read_unlock();
-			local_bh_disable();
-			inet_twsk_deschedule_put(tw);
-			local_bh_enable();
-			goto restart_rcu;
-		}
-		/* If the nulls value we got at the end of this lookup is
-		 * not the expected one, we must restart lookup.
-		 * We probably met an item that was moved to another chain.
-		 */
-		if (get_nulls_value(node) != slot)
-			goto restart;
-		rcu_read_unlock();
-	}
-}
-EXPORT_SYMBOL_GPL(inet_twsk_purge);

net/ipv4/tcp_ipv4.c

@@ -3239,8 +3239,6 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
 {
 	struct net *net;
 
-	inet_twsk_purge(&tcp_hashinfo, AF_INET);
-
 	list_for_each_entry(net, net_exit_list, exit_list)
 		tcp_fastopen_ctx_destroy(net);
 }

net/ipv6/tcp_ipv6.c

@@ -2237,15 +2237,9 @@ static void __net_exit tcpv6_net_exit(struct net *net)
 	inet_ctl_sock_destroy(net->ipv6.tcp_sk);
 }
 
-static void __net_exit tcpv6_net_exit_batch(struct list_head *net_exit_list)
-{
-	inet_twsk_purge(&tcp_hashinfo, AF_INET6);
-}
-
 static struct pernet_operations tcpv6_net_ops = {
 	.init	    = tcpv6_net_init,
 	.exit	    = tcpv6_net_exit,
-	.exit_batch = tcpv6_net_exit_batch,
 };
 
 int __init tcpv6_init(void)