Merge branch 'net-small-csum-optimizations'

Eric Dumazet says:

====================
net: small csum optimizations

After recent x86 csum_partial() optimizations, we can more easily
see in kernel profiles costs of add/adc operations that could
be avoided, by feeding a non zero third argument to csum_partial()
====================

Link: https://lore.kernel.org/r/20211124202446.2917972-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -3485,7 +3485,11 @@ __skb_postpull_rcsum(struct sk_buff *skb, const void *start, unsigned int len,
 static inline void skb_postpull_rcsum(struct sk_buff *skb,
 				      const void *start, unsigned int len)
 {
-	__skb_postpull_rcsum(skb, start, len, 0);
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->csum = ~csum_partial(start, len, ~skb->csum);
+	else if (skb->ip_summed == CHECKSUM_PARTIAL &&
+		 skb_checksum_start_offset(skb) < 0)
+		skb->ip_summed = CHECKSUM_NONE;
 }
 
 static __always_inline void

include/net/gro.h

@@ -173,8 +173,8 @@ static inline void skb_gro_postpull_rcsum(struct sk_buff *skb,
 					const void *start, unsigned int len)
 {
 	if (NAPI_GRO_CB(skb)->csum_valid)
-		NAPI_GRO_CB(skb)->csum = csum_sub(NAPI_GRO_CB(skb)->csum,
-						  csum_partial(start, len, 0));
+		NAPI_GRO_CB(skb)->csum = ~csum_partial(start, len,
+						       ~NAPI_GRO_CB(skb)->csum);
 }
 
 /* GRO checksum functions. These are logical equivalents of the normal