cgroup: net_prio: Do not define task_netpioidx() when not selected

task_netprioidx() should not be defined in case the configuration is
CONFIG_NETPRIO_CGROUP=n. The reason is that in a following patch the
net_prio_subsys_id will only be defined if CONFIG_NETPRIO_CGROUP!=n.
When net_prio is not built at all any callee should only get an empty
task_netprioidx() without any references to net_prio_subsys_id.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: John Fastabend <john.r.fastabend@intel.com>
Cc: netdev@vger.kernel.org
Cc: cgroups@vger.kernel.org

include/net/netprio_cgroup.h

@@ -18,14 +18,13 @@
 #include <linux/rcupdate.h>
 
 
+#if IS_ENABLED(CONFIG_NETPRIO_CGROUP)
 struct netprio_map {
 	struct rcu_head rcu;
 	u32 priomap_len;
 	u32 priomap[];
 };
 
-#ifdef CONFIG_CGROUPS
-
 struct cgroup_netprio_state {
 	struct cgroup_subsys_state css;
 	u32 prioidx;
@@ -71,18 +70,17 @@ static inline u32 task_netprioidx(struct task_struct *p)
 	rcu_read_unlock();
 	return idx;
 }
+#endif
 
-#else
+#else /* !CONFIG_NETPRIO_CGROUP */
 
 static inline u32 task_netprioidx(struct task_struct *p)
 {
 	return 0;
 }
 
+#define sock_update_netprioidx(sk, task)
+
 #endif /* CONFIG_NETPRIO_CGROUP */
 
-#else
-#define sock_update_netprioidx(sk, task)
-#endif
-
 #endif  /* _NET_CLS_CGROUP_H */

net/core/sock.c

@@ -1237,6 +1237,7 @@ void sock_update_classid(struct sock *sk)
 EXPORT_SYMBOL(sock_update_classid);
 #endif
 
+#if IS_ENABLED(CONFIG_NETPRIO_CGROUP)
 void sock_update_netprioidx(struct sock *sk, struct task_struct *task)
 {
 	if (in_interrupt())
@@ -1246,6 +1247,7 @@ void sock_update_netprioidx(struct sock *sk, struct task_struct *task)
 }
 EXPORT_SYMBOL_GPL(sock_update_netprioidx);
 #endif
+#endif
 
 /**
  *	sk_alloc - All socket objects are allocated here