netpoll: use the net namespace of current process instead of init_net

This will allow us to setup netconsole in a different namespace
rather than where init_net is.

Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -1049,8 +1049,10 @@ int netpoll_setup(struct netpoll *np)
 	int err;
 
 	rtnl_lock();
-	if (np->dev_name)
-		ndev = __dev_get_by_name(&init_net, np->dev_name);
+	if (np->dev_name) {
+		struct net *net = current->nsproxy->net_ns;
+		ndev = __dev_get_by_name(net, np->dev_name);
+	}
 	if (!ndev) {
 		np_err(np, "%s doesn't exist, aborting\n", np->dev_name);
 		err = -ENODEV;