linux-kernel - [net-next PATCH v2 04/10] net: ravb: Combine if conditions in RX csum validation

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Message-Id: <20241015133634.193-5-paul.barker.ct@bp.renesas.com>
Date: Tue, 15 Oct 2024 14:36:28 +0100
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Sergey Shtylyov <s.shtylyov@....ru>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Paul Barker <paul.barker.ct@...renesas.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
	Biju Das <biju.das.jz@...renesas.com>,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [net-next PATCH v2 04/10] net: ravb: Combine if conditions in RX csum validation

We can merge the two if conditions on skb_is_nonlinear(). Since
skb_frag_size_sub() and skb_trim() do not free memory, it is still safe
to access the trimmed bytes at the end of the packet after these calls.

Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>
---
 drivers/net/ethernet/renesas/ravb_main.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 4bc2532706c2..2f584c353c78 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -750,7 +750,6 @@ static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 {
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	__wsum csum_proto;
-	skb_frag_t *last_frag;
 	u8 *hw_csum;
 
 	/* The hardware checksum status is contained in sizeof(__sum16) * 2 = 4
@@ -766,21 +765,19 @@ static void ravb_rx_csum_gbeth(struct sk_buff *skb)
 		return;
 
 	if (skb_is_nonlinear(skb)) {
-		last_frag = &shinfo->frags[shinfo->nr_frags - 1];
+		skb_frag_t *last_frag = &shinfo->frags[shinfo->nr_frags - 1];
+
 		hw_csum = skb_frag_address(last_frag) +
 			  skb_frag_size(last_frag);
+		skb_frag_size_sub(last_frag, 2 * sizeof(__sum16));
 	} else {
 		hw_csum = skb_tail_pointer(skb);
+		skb_trim(skb, skb->len - 2 * sizeof(__sum16));
 	}
 
 	hw_csum -= sizeof(__sum16);
 	csum_proto = csum_unfold((__force __sum16)get_unaligned_le16(hw_csum));
 
-	if (skb_is_nonlinear(skb))
-		skb_frag_size_sub(last_frag, 2 * sizeof(__sum16));
-	else
-		skb_trim(skb, skb->len - 2 * sizeof(__sum16));
-
 	if (!csum_proto)
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 }
-- 
2.43.0