sock: add net to prot->enter_memory_pressure callback

The tcp_enter_memory_pressure calls NET_INC_STATS, but doesn't
have where to get the net from.

I decided to add a sk argument, not the net itself, only to factor
all the required sock_net(sk) calls inside the enter_memory_pressure 
callback itself.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 3f4897a..06c5259 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -565,7 +565,7 @@
 #endif
 
 	/* Memory pressure */
-	void			(*enter_memory_pressure)(void);
+	void			(*enter_memory_pressure)(struct sock *sk);
 	atomic_t		*memory_allocated;	/* Current allocated memory. */
 	atomic_t		*sockets_allocated;	/* Current number of sockets. */
 	/*
@@ -1210,7 +1210,7 @@
 
 	page = alloc_pages(sk->sk_allocation, 0);
 	if (!page) {
-		sk->sk_prot->enter_memory_pressure();
+		sk->sk_prot->enter_memory_pressure(sk);
 		sk_stream_moderate_sndbuf(sk);
 	}
 	return page;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4d78818..c25cb52 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -975,7 +975,7 @@
 	ireq->rmt_port = tcp_hdr(skb)->source;
 }
 
-extern void tcp_enter_memory_pressure(void);
+extern void tcp_enter_memory_pressure(struct sock *sk);
 
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 {