[TCP]: Don't set SKB owner in tcp_transmit_skb().

The data itself is already charged to the SKB, doing
the skb_set_owner_w() just generates a lot of noise and
extra atomics we don't really need.

Lmbench improvements on lat_tcp are minimal:

before:
TCP latency using localhost: 23.2701 microseconds
TCP latency using localhost: 23.1994 microseconds
TCP latency using localhost: 23.2257 microseconds

after:
TCP latency using localhost: 22.8380 microseconds
TCP latency using localhost: 22.9465 microseconds
TCP latency using localhost: 22.8462 microseconds

Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 6 insertions, 9 deletions

diff --git a/net/dccp/output.c b/net/dccp/output.c
index 7102e3a..2cc4f4b 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -125,7 +125,7 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
 		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 
 		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
-		err = icsk->icsk_af_ops->queue_xmit(skb, 0);
+		err = icsk->icsk_af_ops->queue_xmit(skb, sk, 0);
 		if (err <= 0)
 			return err;
 
@@ -426,7 +426,7 @@ int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 						      code);
 		if (skb != NULL) {
 			memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
-			err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
+			err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, sk, 0);
 			if (err == NET_XMIT_CN)
 				err = 0;
 		}
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 23633bf..def32d8 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -288,9 +288,8 @@ int ip_output(struct sk_buff *skb)
 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
 }
 
-int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
+int ip_queue_xmit(struct sk_buff *skb, struct sock *sk, int ipfragok)
 {
-	struct sock *sk = skb->sk;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ip_options *opt = inet->opt;
 	struct rtable *rt;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ca40615..f63e99a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -426,7 +426,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 
 	th = (struct tcphdr *) skb_push(skb, tcp_header_size);
 	skb->h.th = th;
-	skb_set_owner_w(skb, sk);
 
 	/* Build TCP header and checksum it. */
 	th->source		= inet->sport;
@@ -479,7 +478,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
 		TCP_INC_STATS(TCP_MIB_OUTSEGS);
 
-	err = icsk->icsk_af_ops->queue_xmit(skb, 0);
+	err = icsk->icsk_af_ops->queue_xmit(skb, sk, 0);
 	if (likely(err <= 0))
 		return err;
 
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index e48fb4c..c598962 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -139,9 +139,8 @@ void inet6_csk_addr2sockaddr(struct sock *sk, struct sockaddr * uaddr)
 
 EXPORT_SYMBOL_GPL(inet6_csk_addr2sockaddr);
 
-int inet6_csk_xmit(struct sk_buff *skb, int ipfragok)
+int inet6_csk_xmit(struct sk_buff *skb, struct sock *sk, int ipfragok)
 {
-	struct sock *sk = skb->sk;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct flowi fl;
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 5b4f82f..c107d45 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -808,7 +808,7 @@ static inline int sctp_v4_xmit(struct sk_buff *skb,
 			  NIPQUAD(((struct rtable *)skb->dst)->rt_dst));
 
 	SCTP_INC_STATS(SCTP_MIB_OUTSCTPPACKS);
-	return ip_queue_xmit(skb, ipfragok);
+	return ip_queue_xmit(skb, skb->sk, ipfragok);
 }
 
 static struct sctp_af sctp_ipv4_specific;