net: add a pre-check of net_ns in sk_change_net()

We do not need to switch the net_ns if the target net_ns the same
as the current one, so here we add a pre-check of net_ns to avoid
this as David suggested.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sock.h b/include/net/sock.h
index 5c3f7c3..9678569 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2252,8 +2252,12 @@ void sock_net_set(struct sock *sk, struct net *net)
  */
 static inline void sk_change_net(struct sock *sk, struct net *net)
 {
-       put_net(sock_net(sk));
-       sock_net_set(sk, hold_net(net));
+       struct net *current_net = sock_net(sk);
+
+       if (!net_eq(current_net, net)) {
+               put_net(current_net);
+               sock_net_set(sk, hold_net(net));
+       }
 }
 
 static inline struct sock *skb_steal_sock(struct sk_buff *skb)