tcp: gro: micro optimizations in tcp[4]_gro_complete()

In tcp_gro_complete() :

Moving the skb->inner_transport_header setting
allows the compiler to reuse the previously loaded value
of skb->transport_header.

Caching skb_shinfo() avoids duplications as well.

In tcp4_gro_complete(), doing a single change on
skb_shinfo(skb)->gso_type also generates better code.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/tcp_offload.c

@@ -299,18 +299,20 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 void tcp_gro_complete(struct sk_buff *skb)
 {
 	struct tcphdr *th = tcp_hdr(skb);
+	struct skb_shared_info *shinfo;
+
+	if (skb->encapsulation)
+		skb->inner_transport_header = skb->transport_header;
 
 	skb->csum_start = (unsigned char *)th - skb->head;
 	skb->csum_offset = offsetof(struct tcphdr, check);
 	skb->ip_summed = CHECKSUM_PARTIAL;
 
-	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
+	shinfo = skb_shinfo(skb);
+	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
 
 	if (th->cwr)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
-
-	if (skb->encapsulation)
-		skb->inner_transport_header = skb->transport_header;
+		shinfo->gso_type |= SKB_GSO_TCP_ECN;
 }
 EXPORT_SYMBOL(tcp_gro_complete);
 
@@ -335,10 +337,9 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 
 	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 				  iph->daddr, 0);
-	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
 
-	if (NAPI_GRO_CB(skb)->is_atomic)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
+	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
+			(NAPI_GRO_CB(skb)->is_atomic * SKB_GSO_TCP_FIXEDID);
 
 	tcp_gro_complete(skb);
 	return 0;