linux-kernel - Re: [PATCH net-next] net: Remove unnecessary intermediate variables

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Message-ID: <ae154f9a96a710157f9b402ba21c6888c855dd1e.camel@perches.com>
Date:   Sat, 22 Aug 2020 13:39:28 -0700
From:   Joe Perches <joe@...ches.com>
To:     David Miller <davem@...emloft.net>, Jianlin.Lv@....com
Cc:     netdev@...r.kernel.org, kuba@...nel.org, Song.Zhu@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: Remove unnecessary intermediate variables

On Sat, 2020-08-22 at 12:33 -0700, David Miller wrote:
> From: Jianlin Lv <Jianlin.Lv@....com>
> Date: Sat, 22 Aug 2020 10:04:31 +0800
> 
> > It is not necessary to use src/dst as an intermediate variable for
> > assignment operation; Delete src/dst intermediate variables to avoid
> > unnecessary variable declarations.
> > 
> > Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>
> 
> It keeps the line lengths within reasonable length, so these local
> variables are fine.
> 
> Also, the appropriate subsystem prefix for this patch should be "vxlan: "
> not "net: " in your Subject line.  If someone is skimming the shortlog
> in 'git' how will they tell where exactly in the networking your change
> is being made?
> 
> Anyways, I'm not applying this, thanks.

It _might_ be slightly faster to use inlines
instead so there's less copy of 16 byte structs
on the ipv6 side.

It's slightly smaller object code.
---
 drivers/net/vxlan.c | 46 ++++++++++++++++++++++++++--------------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index b9fefe27e3e8..e0ea246b3678 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -95,7 +95,25 @@ static inline bool vxlan_collect_metadata(struct vxlan_sock *vs)
 	       ip_tunnel_collect_metadata();
 }
 
+static __always_inline
+void vxlan_use_v4_addrs(struct ip_tunnel_info *info,
+			union vxlan_addr *remote_ip,
+			union vxlan_addr *local_ip)
+{
+	info->key.u.ipv4.src = remote_ip->sin.sin_addr.s_addr;
+	info->key.u.ipv4.dst = local_ip->sin.sin_addr.s_addr;
+}
+
 #if IS_ENABLED(CONFIG_IPV6)
+static __always_inline
+void vxlan_use_v6_addrs(struct ip_tunnel_info *info,
+			union vxlan_addr *remote_ip,
+			union vxlan_addr *local_ip)
+{
+	info->key.u.ipv6.src = remote_ip->sin6.sin6_addr;
+	info->key.u.ipv6.dst = local_ip->sin6.sin6_addr;
+}
+
 static inline
 bool vxlan_addr_equal(const union vxlan_addr *a, const union vxlan_addr *b)
 {
@@ -2724,17 +2742,11 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		ndst = &rt->dst;
 		err = skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM,
 					    netif_is_any_bridge_port(dev));
-		if (err < 0) {
+		if (err < 0)
 			goto tx_error;
-		} else if (err) {
-			if (info) {
-				struct in_addr src, dst;
-
-				src = remote_ip.sin.sin_addr;
-				dst = local_ip.sin.sin_addr;
-				info->key.u.ipv4.src = src.s_addr;
-				info->key.u.ipv4.dst = dst.s_addr;
-			}
+		if (err) {	/* newly built encapsulation length */
+			if (info)
+				vxlan_use_v4_addrs(info, &remote_ip, &local_ip);
 			vxlan_encap_bypass(skb, vxlan, vxlan, vni, false);
 			dst_release(ndst);
 			goto out_unlock;
@@ -2780,17 +2792,11 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 
 		err = skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM,
 					    netif_is_any_bridge_port(dev));
-		if (err < 0) {
+		if (err < 0)
 			goto tx_error;
-		} else if (err) {
-			if (info) {
-				struct in6_addr src, dst;
-
-				src = remote_ip.sin6.sin6_addr;
-				dst = local_ip.sin6.sin6_addr;
-				info->key.u.ipv6.src = src;
-				info->key.u.ipv6.dst = dst;
-			}
+		if (err) {	/* newly built encapsulation length */
+			if (info)
+				vxlan_use_v6_addrs(info, &remote_ip, &local_ip);
 
 			vxlan_encap_bypass(skb, vxlan, vxlan, vni, false);
 			dst_release(ndst);