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Date: Wed, 27 May 2009 14:50:28 +1000
From: Herbert Xu <herbert@...dor.apana.org.au>
To: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: [PATCH 9/14] gro: Avoid unnecessary comparison after skb_gro_header
gro: Avoid unnecessary comparison after skb_gro_header
For the overwhelming majority of cases, skb_gro_header's return
value cannot be NULL. Yet we must check it because of its current
form. This patch splits it up into multiple functions in order
to avoid this.
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---
include/linux/netdevice.h | 23 ++++++++++++++---------
net/core/dev.c | 17 ++++++++++++-----
net/ipv4/af_inet.c | 13 ++++++++++---
net/ipv4/tcp.c | 22 ++++++++++++++++------
net/ipv6/af_inet6.c | 13 ++++++++++---
5 files changed, 62 insertions(+), 26 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 966c413..d2b1561 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1132,18 +1132,23 @@ static inline void skb_gro_pull(struct sk_buff *skb, unsigned int len)
NAPI_GRO_CB(skb)->data_offset += len;
}
-static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
+static inline void *skb_gro_header_fast(struct sk_buff *skb,
+ unsigned int offset)
{
- unsigned int offset = skb_gro_offset(skb);
+ return NAPI_GRO_CB(skb)->frag0 + offset;
+}
- hlen += offset;
- if (NAPI_GRO_CB(skb)->frag0_len < hlen) {
- NAPI_GRO_CB(skb)->frag0 = NULL;
- NAPI_GRO_CB(skb)->frag0_len = 0;
- return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
- }
+static inline int skb_gro_header_hard(struct sk_buff *skb, unsigned int hlen)
+{
+ return NAPI_GRO_CB(skb)->frag0_len < hlen;
+}
- return NAPI_GRO_CB(skb)->frag0 + offset;
+static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
+ unsigned int offset)
+{
+ NAPI_GRO_CB(skb)->frag0 = NULL;
+ NAPI_GRO_CB(skb)->frag0_len = 0;
+ return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
}
static inline void *skb_gro_mac_header(struct sk_buff *skb)
diff --git a/net/core/dev.c b/net/core/dev.c
index e634c8a..5a81302 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2587,17 +2587,24 @@ struct sk_buff *napi_frags_skb(struct napi_struct *napi)
{
struct sk_buff *skb = napi->skb;
struct ethhdr *eth;
+ unsigned int hlen;
+ unsigned int off;
napi->skb = NULL;
skb_reset_mac_header(skb);
skb_gro_reset_offset(skb);
- eth = skb_gro_header(skb, sizeof(*eth));
- if (!eth) {
- napi_reuse_skb(napi, skb);
- skb = NULL;
- goto out;
+ off = skb_gro_offset(skb);
+ hlen = off + sizeof(*eth);
+ eth = skb_gro_header_fast(skb, off);
+ if (skb_gro_header_hard(skb, hlen)) {
+ eth = skb_gro_header_slow(skb, hlen, off);
+ if (unlikely(!eth)) {
+ napi_reuse_skb(napi, skb);
+ skb = NULL;
+ goto out;
+ }
}
skb_gro_pull(skb, sizeof(*eth));
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 1706896..644cc55 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1246,13 +1246,20 @@ static struct sk_buff **inet_gro_receive(struct sk_buff **head,
struct sk_buff **pp = NULL;
struct sk_buff *p;
struct iphdr *iph;
+ unsigned int hlen;
+ unsigned int off;
int flush = 1;
int proto;
int id;
- iph = skb_gro_header(skb, sizeof(*iph));
- if (unlikely(!iph))
- goto out;
+ off = skb_gro_offset(skb);
+ hlen = off + sizeof(*iph);
+ iph = skb_gro_header_fast(skb, off);
+ if (skb_gro_header_hard(skb, hlen)) {
+ iph = skb_gro_header_slow(skb, hlen, off);
+ if (unlikely(!iph))
+ goto out;
+ }
proto = iph->protocol & (MAX_INET_PROTOS - 1);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 68342d4..c3dcec5 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2518,20 +2518,30 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
unsigned int thlen;
unsigned int flags;
unsigned int mss = 1;
+ unsigned int hlen;
+ unsigned int off;
int flush = 1;
int i;
- th = skb_gro_header(skb, sizeof(*th));
- if (unlikely(!th))
- goto out;
+ off = skb_gro_offset(skb);
+ hlen = off + sizeof(*th);
+ th = skb_gro_header_fast(skb, off);
+ if (skb_gro_header_hard(skb, hlen)) {
+ th = skb_gro_header_slow(skb, hlen, off);
+ if (unlikely(!th))
+ goto out;
+ }
thlen = th->doff * 4;
if (thlen < sizeof(*th))
goto out;
- th = skb_gro_header(skb, thlen);
- if (unlikely(!th))
- goto out;
+ hlen = off + thlen;
+ if (skb_gro_header_hard(skb, hlen)) {
+ th = skb_gro_header_slow(skb, hlen, off);
+ if (unlikely(!th))
+ goto out;
+ }
skb_gro_pull(skb, thlen);
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 61f5538..b6215be 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -817,13 +817,20 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
struct sk_buff *p;
struct ipv6hdr *iph;
unsigned int nlen;
+ unsigned int hlen;
+ unsigned int off;
int flush = 1;
int proto;
__wsum csum;
- iph = skb_gro_header(skb, sizeof(*iph));
- if (unlikely(!iph))
- goto out;
+ off = skb_gro_offset(skb);
+ hlen = off + sizeof(*iph);
+ iph = skb_gro_header_fast(skb, off);
+ if (skb_gro_header_hard(skb, hlen)) {
+ iph = skb_gro_header_slow(skb, hlen, off);
+ if (unlikely(!iph))
+ goto out;
+ }
skb_gro_pull(skb, sizeof(*iph));
skb_set_transport_header(skb, skb_gro_offset(skb));
--
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