netdev - [PATCH net-next] ipv6: Optimize ipv6_change

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Message-ID: <50EC4D8C.2080408@linux-ipv6.org>
Date:	Wed, 09 Jan 2013 01:47:08 +0900
From:	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
To:	davem@...emloft.net, netdev@...r.kernel.org
CC:	yoshfuji@...ux-ipv6.org
Subject: [PATCH net-next] ipv6: Optimize ipv6_change_dsfield().

Do not convert endian back and forth.
If the caller uses contant "mask" argument (and most callers do),
we can omit runtime endian conversion here.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
---
 include/net/dsfield.h |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/net/dsfield.h b/include/net/dsfield.h
index 8a8d4e0..e1ad903 100644
--- a/include/net/dsfield.h
+++ b/include/net/dsfield.h
@@ -43,11 +43,9 @@ static inline void ipv4_change_dsfield(struct iphdr *iph,__u8 mask,
 static inline void ipv6_change_dsfield(struct ipv6hdr *ipv6h,__u8 mask,
     __u8 value)
 {
-        __u16 tmp;
+	__be16 *p = (__force __be16 *)ipv6h;

-	tmp = ntohs(*(__be16 *) ipv6h);
-	tmp = (tmp & ((mask << 4) | 0xf00f)) | (value << 4);
-	*(__be16 *) ipv6h = htons(tmp);
+	*p = (*p & htons((((u16)mask << 4) | 0xf00f))) | htons((u16)value << 4);
 }

-- 
1.7.9.5

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