net: tcp_memcontrol: protect all tcp_memcontrol calls by jump-label

Move the jump-label from sock_update_memcg() and sock_release_memcg() to
the callsite, and so eliminate those function calls when socket
accounting is not enabled.

This also eliminates the need for dummy functions because the calls will
be optimized away if the Kconfig options are not enabled.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -694,17 +694,8 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
 struct sock;
-#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
 void sock_update_memcg(struct sock *sk);
 void sock_release_memcg(struct sock *sk);
-#else
-static inline void sock_update_memcg(struct sock *sk)
-{
-}
-static inline void sock_release_memcg(struct sock *sk)
-{
-}
-#endif /* CONFIG_INET && CONFIG_MEMCG_KMEM */
 
 #ifdef CONFIG_MEMCG_KMEM
 extern struct static_key memcg_kmem_enabled_key;

mm/memcontrol.c

@@ -293,46 +293,40 @@ static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
 
 void sock_update_memcg(struct sock *sk)
 {
-	if (mem_cgroup_sockets_enabled) {
-		struct mem_cgroup *memcg;
-		struct cg_proto *cg_proto;
+	struct mem_cgroup *memcg;
+	struct cg_proto *cg_proto;
 
-		BUG_ON(!sk->sk_prot->proto_cgroup);
+	BUG_ON(!sk->sk_prot->proto_cgroup);
 
-		/* Socket cloning can throw us here with sk_cgrp already
-		 * filled. It won't however, necessarily happen from
-		 * process context. So the test for root memcg given
-		 * the current task's memcg won't help us in this case.
-		 *
-		 * Respecting the original socket's memcg is a better
-		 * decision in this case.
-		 */
-		if (sk->sk_cgrp) {
-			BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
-			css_get(&sk->sk_cgrp->memcg->css);
-			return;
-		}
+	/* Socket cloning can throw us here with sk_cgrp already
+	 * filled. It won't however, necessarily happen from
+	 * process context. So the test for root memcg given
+	 * the current task's memcg won't help us in this case.
+	 *
+	 * Respecting the original socket's memcg is a better
+	 * decision in this case.
+	 */
+	if (sk->sk_cgrp) {
+		BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
+		css_get(&sk->sk_cgrp->memcg->css);
+		return;
+	}
 
-		rcu_read_lock();
-		memcg = mem_cgroup_from_task(current);
-		cg_proto = sk->sk_prot->proto_cgroup(memcg);
-		if (cg_proto && cg_proto->active &&
-		    css_tryget_online(&memcg->css)) {
-			sk->sk_cgrp = cg_proto;
-		}
-		rcu_read_unlock();
+	rcu_read_lock();
+	memcg = mem_cgroup_from_task(current);
+	cg_proto = sk->sk_prot->proto_cgroup(memcg);
+	if (cg_proto && cg_proto->active &&
+	    css_tryget_online(&memcg->css)) {
+		sk->sk_cgrp = cg_proto;
 	}
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(sock_update_memcg);
 
 void sock_release_memcg(struct sock *sk)
 {
-	if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
-		struct mem_cgroup *memcg;
-		WARN_ON(!sk->sk_cgrp->memcg);
-		memcg = sk->sk_cgrp->memcg;
-		css_put(&sk->sk_cgrp->memcg->css);
-	}
+	WARN_ON(!sk->sk_cgrp->memcg);
+	css_put(&sk->sk_cgrp->memcg->css);
 }
 
 struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)

net/core/sock.c

@@ -1507,12 +1507,6 @@ void sk_free(struct sock *sk)
 }
 EXPORT_SYMBOL(sk_free);
 
-static void sk_update_clone(const struct sock *sk, struct sock *newsk)
-{
-	if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
-		sock_update_memcg(newsk);
-}
-
 /**
  *	sk_clone_lock - clone a socket, and lock its clone
  *	@sk: the socket to clone
@@ -1607,7 +1601,8 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 		sk_set_socket(newsk, NULL);
 		newsk->sk_wq = NULL;
 
-		sk_update_clone(sk, newsk);
+		if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
+			sock_update_memcg(newsk);
 
 		if (newsk->sk_prot->sockets_allocated)
 			sk_sockets_allocated_inc(newsk);

net/ipv4/tcp.c

@@ -422,7 +422,8 @@ void tcp_init_sock(struct sock *sk)
 	sk->sk_rcvbuf = sysctl_tcp_rmem[1];
 
 	local_bh_disable();
-	sock_update_memcg(sk);
+	if (mem_cgroup_sockets_enabled)
+		sock_update_memcg(sk);
 	sk_sockets_allocated_inc(sk);
 	local_bh_enable();
 }

net/ipv4/tcp_ipv4.c

@@ -1818,7 +1818,9 @@ void tcp_v4_destroy_sock(struct sock *sk)
 	tcp_saved_syn_free(tp);
 
 	sk_sockets_allocated_dec(sk);
-	sock_release_memcg(sk);
+
+	if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
+		sock_release_memcg(sk);
 }
 EXPORT_SYMBOL(tcp_v4_destroy_sock);