net: cgroup: Guard users of sock_cgroup_classid()

Exclude code that relies on sock_cgroup_classid() as preparation of
removal of the function.

Signed-off-by: Michal Koutný <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/ipv4/inet_diag.c

···
 	    ext & (1 << (INET_DIAG_TCLASS - 1))) {
 		u32 classid = 0;
 
-#ifdef CONFIG_SOCK_CGROUP_DATA
+#ifdef CONFIG_CGROUP_NET_CLASSID
 		classid = sock_cgroup_classid(&sk->sk_cgrp_data);
 #endif
 		/* Fallback to socket priority if class id isn't set.

net/netfilter/xt_cgroup.c

···
 static bool
 cgroup_mt_v0(const struct sk_buff *skb, struct xt_action_param *par)
 {
+#ifdef CONFIG_CGROUP_NET_CLASSID
 	const struct xt_cgroup_info_v0 *info = par->matchinfo;
 	struct sock *sk = skb->sk;
 
···
 
 	return (info->id == sock_cgroup_classid(&skb->sk->sk_cgrp_data)) ^
 		info->invert;
+#endif
+	return false;
 }
 
 static bool cgroup_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
···
 	if (ancestor)
 		return cgroup_is_descendant(sock_cgroup_ptr(skcd), ancestor) ^
 			info->invert_path;
+#ifdef CONFIG_CGROUP_NET_CLASSID
 	else
 		return (info->classid == sock_cgroup_classid(skcd)) ^
 			info->invert_classid;
+#endif
+	return false;
 }
 
 static bool cgroup_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
···
 	if (ancestor)
 		return cgroup_is_descendant(sock_cgroup_ptr(skcd), ancestor) ^
 			info->invert_path;
+#ifdef CONFIG_CGROUP_NET_CLASSID
 	else
 		return (info->classid == sock_cgroup_classid(skcd)) ^
 			info->invert_classid;
+#endif
+	return false;
 }
 
 static void cgroup_mt_destroy_v1(const struct xt_mtdtor_param *par)