linux-kernel - [PATCH net-next v2] gro: avoid checking for a failed search

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Date:   Tue, 8 Nov 2022 13:33:28 +0100
From:   Richard Gobert <richardbgobert@...il.com>
To:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, lixiaoyan@...gle.com, alexanderduyck@...com,
        steffen.klassert@...unet.com, richardbgobert@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next v2] gro: avoid checking for a failed search

After searching for a protocol handler in dev_gro_receive, checking for
failure is redundant. Skip the failure code after finding the 
corresponding handler.

Suggested-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Richard Gobert <richardbgobert@...il.com>
---
 net/core/gro.c | 72 +++++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 36 deletions(-)

diff --git a/net/core/gro.c b/net/core/gro.c
index bc9451743307..8e0fe85a647d 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -489,45 +489,45 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(ptype, head, list) {
-		if (ptype->type != type || !ptype->callbacks.gro_receive)
-			continue;
-
-		skb_set_network_header(skb, skb_gro_offset(skb));
-		skb_reset_mac_len(skb);
-		BUILD_BUG_ON(sizeof_field(struct napi_gro_cb, zeroed) != sizeof(u32));
-		BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
-					 sizeof(u32))); /* Avoid slow unaligned acc */
-		*(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0;
-		NAPI_GRO_CB(skb)->flush = skb_has_frag_list(skb);
-		NAPI_GRO_CB(skb)->is_atomic = 1;
-		NAPI_GRO_CB(skb)->count = 1;
-		if (unlikely(skb_is_gso(skb))) {
-			NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs;
-			/* Only support TCP at the moment. */
-			if (!skb_is_gso_tcp(skb))
-				NAPI_GRO_CB(skb)->flush = 1;
-		}
-
-		/* Setup for GRO checksum validation */
-		switch (skb->ip_summed) {
-		case CHECKSUM_COMPLETE:
-			NAPI_GRO_CB(skb)->csum = skb->csum;
-			NAPI_GRO_CB(skb)->csum_valid = 1;
-			break;
-		case CHECKSUM_UNNECESSARY:
-			NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
-			break;
-		}
-
-		pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
-					ipv6_gro_receive, inet_gro_receive,
-					&gro_list->list, skb);
-		break;
+		if (ptype->type == type && ptype->callbacks.gro_receive)
+			goto found_ptype;
 	}
 	rcu_read_unlock();
+	goto normal;
 
-	if (&ptype->list == head)
-		goto normal;
+found_ptype:
+	skb_set_network_header(skb, skb_gro_offset(skb));
+	skb_reset_mac_len(skb);
+	BUILD_BUG_ON(sizeof_field(struct napi_gro_cb, zeroed) != sizeof(u32));
+	BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
+					sizeof(u32))); /* Avoid slow unaligned acc */
+	*(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0;
+	NAPI_GRO_CB(skb)->flush = skb_has_frag_list(skb);
+	NAPI_GRO_CB(skb)->is_atomic = 1;
+	NAPI_GRO_CB(skb)->count = 1;
+	if (unlikely(skb_is_gso(skb))) {
+		NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs;
+		/* Only support TCP at the moment. */
+		if (!skb_is_gso_tcp(skb))
+			NAPI_GRO_CB(skb)->flush = 1;
+	}
+
+	/* Setup for GRO checksum validation */
+	switch (skb->ip_summed) {
+	case CHECKSUM_COMPLETE:
+		NAPI_GRO_CB(skb)->csum = skb->csum;
+		NAPI_GRO_CB(skb)->csum_valid = 1;
+		break;
+	case CHECKSUM_UNNECESSARY:
+		NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
+		break;
+	}
+
+	pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
+				ipv6_gro_receive, inet_gro_receive,
+				&gro_list->list, skb);
+
+	rcu_read_unlock();
 
 	if (PTR_ERR(pp) == -EINPROGRESS) {
 		ret = GRO_CONSUMED;
-- 
2.20.1