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Commit a5b1cf28 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
Browse files

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: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7489594c

include/linux/netdevice.h

+14 −9
Original line number Diff line number Diff line
@@ -1132,20 +1132,25 @@ 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;

}



static inline int skb_gro_header_hard(struct sk_buff *skb, unsigned int hlen)

{

	return NAPI_GRO_CB(skb)->frag0_len < hlen;

}



	hlen += offset;

	if (NAPI_GRO_CB(skb)->frag0_len < hlen) {

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;

}



	return NAPI_GRO_CB(skb)->frag0 + offset;

}



static inline void *skb_gro_mac_header(struct sk_buff *skb)

{

	return NAPI_GRO_CB(skb)->frag0 ?: skb_mac_header(skb);

net/core/dev.c

+12 −5
Original line number Diff line number Diff line
@@ -2590,18 +2590,25 @@ 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) {

	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));

net/ipv4/af_inet.c

+10 −3
Original line number Diff line number Diff line
@@ -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));

	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);

net/ipv4/tcp.c

+16 −6
Original line number Diff line number Diff line
@@ -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));

	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);

	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);

net/ipv6/af_inet6.c

+10 −3
Original line number Diff line number Diff line
@@ -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));

	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));