[NET]: Tiny af_packet.c cleanup.

net/packet/af_packet.c

@@ -381,6 +381,23 @@ static int packet_sendmsg_spkt(struct kiocb *iocb, struct socket *sock,
 }
 #endif
 
+static inline unsigned run_filter(struct sk_buff *skb, struct sock *sk, unsigned res)
+{
+	struct sk_filter *filter;
+
+	bh_lock_sock(sk);
+	filter = sk->sk_filter;
+	/*
+	 * Our caller already checked that filter != NULL but we need to
+	 * verify that under bh_lock_sock() to be safe
+	 */
+	if (likely(filter != NULL))
+		res = sk_run_filter(skb, filter->insns, filter->len);
+	bh_unlock_sock(sk);
+
+	return res;
+}
+
 /*
    This function makes lazy skb cloning in hope that most of packets
    are discarded by BPF.
@@ -429,15 +446,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,  struct packe
 	snaplen = skb->len;
 
 	if (sk->sk_filter) {
-		unsigned res = snaplen;
-		struct sk_filter *filter;
-
-		bh_lock_sock(sk);
-		if ((filter = sk->sk_filter) != NULL)
-			res = sk_run_filter(skb, sk->sk_filter->insns,
-					    sk->sk_filter->len);
-		bh_unlock_sock(sk);
-
+		unsigned res = run_filter(skb, sk, snaplen);
 		if (res == 0)
 			goto drop_n_restore;
 		if (snaplen > res)
@@ -533,15 +542,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,  struct pack
 	snaplen = skb->len;
 
 	if (sk->sk_filter) {
-		unsigned res = snaplen;
-		struct sk_filter *filter;
-
-		bh_lock_sock(sk);
-		if ((filter = sk->sk_filter) != NULL)
-			res = sk_run_filter(skb, sk->sk_filter->insns,
-					    sk->sk_filter->len);
-		bh_unlock_sock(sk);
-
+		unsigned res = run_filter(skb, sk, snaplen);
 		if (res == 0)
 			goto drop_n_restore;
 		if (snaplen > res)