[SK_BUFF]: Convert skb->tail to sk_buff_data_t

So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)

Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 30 insertions, 23 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 6562e57..86dc9f6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1069,7 +1069,7 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 			skb_reset_mac_header(skb2);
 
 			if (skb_network_header(skb2) < skb2->data ||
-			    skb_network_header(skb2) > skb2->tail) {
+			    skb2->network_header > skb2->tail) {
 				if (net_ratelimit())
 					printk(KERN_CRIT "protocol %04x is "
 					       "buggy, dev %s\n",
@@ -1175,7 +1175,7 @@ int skb_checksum_help(struct sk_buff *skb)
 	BUG_ON(offset > (int)skb->len);
 	csum = skb_checksum(skb, offset, skb->len-offset, 0);
 
-	offset = skb->tail - skb_transport_header(skb);
+	offset = skb->tail - skb->transport_header;
 	BUG_ON(offset <= 0);
 	BUG_ON(skb->csum_offset + 2 > offset);
 
diff --git a/net/core/filter.c b/net/core/filter.c
index d2358a5..bd903aa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -46,7 +46,7 @@ static void *__load_pointer(struct sk_buff *skb, int k)
 	else if (k >= SKF_LL_OFF)
 		ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
 
-	if (ptr >= skb->head && ptr < skb->tail)
+	if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
 		return ptr;
 	return NULL;
 }
diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index 259473d..bcc2559 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -61,7 +61,7 @@ gnet_stats_start_copy_compat(struct sk_buff *skb, int type, int tc_stats_type,
 	spin_lock_bh(lock);
 	d->lock = lock;
 	if (type)
-		d->tail = (struct rtattr *) skb->tail;
+		d->tail = (struct rtattr *)skb_tail_pointer(skb);
 	d->skb = skb;
 	d->compat_tc_stats = tc_stats_type;
 	d->compat_xstats = xstats_type;
@@ -212,7 +212,7 @@ int
 gnet_stats_finish_copy(struct gnet_dump *d)
 {
 	if (d->tail)
-		d->tail->rta_len = d->skb->tail - (u8 *) d->tail;
+		d->tail->rta_len = skb_tail_pointer(d->skb) - (u8 *)d->tail;
 
 	if (d->compat_tc_stats)
 		if (gnet_stats_copy(d, d->compat_tc_stats, &d->tc_stats,
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 9da8357..f9469ea 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2357,7 +2357,7 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
 		*vlan_encapsulated_proto = htons(ETH_P_IP);
 	}
 
-	skb_set_network_header(skb, skb->tail - skb->data);
+	skb->network_header = skb->tail;
 	skb->transport_header = skb->network_header + sizeof(struct iphdr);
 	skb_put(skb, sizeof(struct iphdr) + sizeof(struct udphdr));
 
@@ -2696,7 +2696,7 @@ static struct sk_buff *fill_packet_ipv6(struct net_device *odev,
 		*vlan_encapsulated_proto = htons(ETH_P_IPV6);
 	}
 
-	skb_set_network_header(skb, skb->tail - skb->data);
+	skb->network_header = skb->tail;
 	skb->transport_header = skb->network_header + sizeof(struct ipv6hdr);
 	skb_put(skb, sizeof(struct ipv6hdr) + sizeof(struct udphdr));
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a48b086..ddcbc4d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -87,8 +87,9 @@ static struct kmem_cache *skbuff_fclone_cache __read_mostly;
 void skb_over_panic(struct sk_buff *skb, int sz, void *here)
 {
 	printk(KERN_EMERG "skb_over_panic: text:%p len:%d put:%d head:%p "
-			  "data:%p tail:%p end:%p dev:%s\n",
-	       here, skb->len, sz, skb->head, skb->data, skb->tail, skb->end,
+			  "data:%p tail:%#lx end:%p dev:%s\n",
+	       here, skb->len, sz, skb->head, skb->data,
+	       (unsigned long)skb->tail, skb->end,
 	       skb->dev ? skb->dev->name : "<NULL>");
 	BUG();
 }
@@ -105,8 +106,9 @@ void skb_over_panic(struct sk_buff *skb, int sz, void *here)
 void skb_under_panic(struct sk_buff *skb, int sz, void *here)
 {
 	printk(KERN_EMERG "skb_under_panic: text:%p len:%d put:%d head:%p "
-			  "data:%p tail:%p end:%p dev:%s\n",
-	       here, skb->len, sz, skb->head, skb->data, skb->tail, skb->end,
+			  "data:%p tail:%#lx end:%p dev:%s\n",
+	       here, skb->len, sz, skb->head, skb->data,
+	       (unsigned long)skb->tail, skb->end,
 	       skb->dev ? skb->dev->name : "<NULL>");
 	BUG();
 }
@@ -167,7 +169,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	atomic_set(&skb->users, 1);
 	skb->head = data;
 	skb->data = data;
-	skb->tail = data;
+	skb_reset_tail_pointer(skb);
 	skb->end  = data + size;
 	/* make sure we initialize shinfo sequentially */
 	shinfo = skb_shinfo(skb);
@@ -629,7 +631,12 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 
 	/* Copy only real data... and, alas, header. This should be
 	 * optimized for the cases when header is void. */
-	memcpy(data + nhead, skb->head, skb->tail - skb->head);
+	memcpy(data + nhead, skb->head,
+		skb->tail
+#ifndef NET_SKBUFF_DATA_USES_OFFSET
+		- skb->head
+#endif
+		);
 	memcpy(data + size, skb->end, sizeof(struct skb_shared_info));
 
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
@@ -645,9 +652,9 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 	skb->head     = data;
 	skb->end      = data + size;
 	skb->data    += off;
-	skb->tail    += off;
 #ifndef NET_SKBUFF_DATA_USES_OFFSET
-	/* {transport,network,mac}_header are relative to skb->head */
+	/* {transport,network,mac}_header and tail are relative to skb->head */
+	skb->tail	      += off;
 	skb->transport_header += off;
 	skb->network_header   += off;
 	skb->mac_header	      += off;
@@ -762,7 +769,7 @@ int skb_pad(struct sk_buff *skb, int pad)
 		return 0;
 	}
 
-	ntail = skb->data_len + pad - (skb->end - skb->tail);
+	ntail = skb->data_len + pad - (skb->end - skb_tail_pointer(skb));
 	if (likely(skb_cloned(skb) || ntail > 0)) {
 		err = pskb_expand_head(skb, 0, ntail, GFP_ATOMIC);
 		if (unlikely(err))
@@ -863,7 +870,7 @@ done:
 	} else {
 		skb->len       = len;
 		skb->data_len  = 0;
-		skb->tail      = skb->data + len;
+		skb_set_tail_pointer(skb, len);
 	}
 
 	return 0;
@@ -900,7 +907,7 @@ unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
 	 * plus 128 bytes for future expansions. If we have enough
 	 * room at tail, reallocate without expansion only if skb is cloned.
 	 */
-	int i, k, eat = (skb->tail + delta) - skb->end;
+	int i, k, eat = (skb_tail_pointer(skb) + delta) - skb->end;
 
 	if (eat > 0 || skb_cloned(skb)) {
 		if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
@@ -908,7 +915,7 @@ unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
 			return NULL;
 	}
 
-	if (skb_copy_bits(skb, skb_headlen(skb), skb->tail, delta))
+	if (skb_copy_bits(skb, skb_headlen(skb), skb_tail_pointer(skb), delta))
 		BUG();
 
 	/* Optimization: no fragments, no reasons to preestimate
@@ -1004,7 +1011,7 @@ pull_pages:
 	skb->tail     += delta;
 	skb->data_len -= delta;
 
-	return skb->tail;
+	return skb_tail_pointer(skb);
 }
 
 /* Copy some data bits from skb to kernel buffer. */
@@ -1539,7 +1546,7 @@ static inline void skb_split_inside_header(struct sk_buff *skb,
 	skb1->len		   += skb1->data_len;
 	skb->data_len		   = 0;
 	skb->len		   = len;
-	skb->tail		   = skb->data + len;
+	skb_set_tail_pointer(skb, len);
 }
 
 static inline void skb_split_no_header(struct sk_buff *skb,
diff --git a/net/core/wireless.c b/net/core/wireless.c
index 7c6a5db..4a777b6 100644
--- a/net/core/wireless.c
+++ b/net/core/wireless.c
@@ -1938,7 +1938,7 @@ static inline int rtnetlink_fill_iwinfo(struct sk_buff *	skb,
 {
 	struct ifinfomsg *r;
 	struct nlmsghdr  *nlh;
-	unsigned char	 *b = skb->tail;
+	unsigned char	 *b = skb_tail_pointer(skb);
 
 	nlh = NLMSG_PUT(skb, 0, 0, type, sizeof(*r));
 	r = NLMSG_DATA(nlh);
@@ -1952,7 +1952,7 @@ static inline int rtnetlink_fill_iwinfo(struct sk_buff *	skb,
 	/* Add the wireless events in the netlink packet */
 	RTA_PUT(skb, IFLA_WIRELESS, event_len, event);
 
-	nlh->nlmsg_len = skb->tail - b;
+	nlh->nlmsg_len = skb_tail_pointer(skb) - b;
 	return skb->len;
 
 nlmsg_failure: