[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>

5 files changed, 11 insertions, 11 deletions

diff --git a/drivers/usb/atm/usbatm.c b/drivers/usb/atm/usbatm.c
index ec63b0ee074..4d8f282b23d 100644
--- a/drivers/usb/atm/usbatm.c
+++ b/drivers/usb/atm/usbatm.c
@@ -335,15 +335,15 @@ static void usbatm_extract_one_cell(struct usbatm_data *instance, unsigned char
 
 	sarb = instance->cached_vcc->sarb;
 
-	if (sarb->tail + ATM_CELL_PAYLOAD > sarb->end) {
+	if (skb_tail_pointer(sarb) + ATM_CELL_PAYLOAD > sarb->end) {
 		atm_rldbg(instance, "%s: buffer overrun (sarb->len %u, vcc: 0x%p)!\n",
 				__func__, sarb->len, vcc);
 		/* discard cells already received */
 		skb_trim(sarb, 0);
-		UDSL_ASSERT(sarb->tail + ATM_CELL_PAYLOAD <= sarb->end);
+		UDSL_ASSERT(skb_tail_pointer(sarb) + ATM_CELL_PAYLOAD <= sarb->end);
 	}
 
-	memcpy(sarb->tail, source + ATM_CELL_HEADER, ATM_CELL_PAYLOAD);
+	memcpy(skb_tail_pointer(sarb), source + ATM_CELL_HEADER, ATM_CELL_PAYLOAD);
 	__skb_put(sarb, ATM_CELL_PAYLOAD);
 
 	if (pti & 1) {
@@ -370,7 +370,7 @@ static void usbatm_extract_one_cell(struct usbatm_data *instance, unsigned char
 			goto out;
 		}
 
-		if (crc32_be(~0, sarb->tail - pdu_length, pdu_length) != 0xc704dd7b) {
+		if (crc32_be(~0, skb_tail_pointer(sarb) - pdu_length, pdu_length) != 0xc704dd7b) {
 			atm_rldbg(instance, "%s: packet failed crc check (vcc: 0x%p)!\n",
 				  __func__, vcc);
 			atomic_inc(&vcc->stats->rx_err);
@@ -396,7 +396,7 @@ static void usbatm_extract_one_cell(struct usbatm_data *instance, unsigned char
 			goto out;	/* atm_charge increments rx_drop */
 		}
 
-		memcpy(skb->data, sarb->tail - pdu_length, length);
+		memcpy(skb->data, skb_tail_pointer(sarb) - pdu_length, length);
 		__skb_put(skb, length);
 
 		vdbg("%s: sending skb 0x%p, skb->len %u, skb->truesize %u",
diff --git a/drivers/usb/net/asix.c b/drivers/usb/net/asix.c
index 5808ea08245..f56e2dab371 100644
--- a/drivers/usb/net/asix.c
+++ b/drivers/usb/net/asix.c
@@ -298,7 +298,7 @@ static int asix_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 		if (ax_skb) {
 			ax_skb->len = size;
 			ax_skb->data = packet;
-			ax_skb->tail = packet + size;
+			skb_set_tail_pointer(ax_skb, size);
 			usbnet_skb_return(dev, ax_skb);
 		} else {
 			return 0;
@@ -338,7 +338,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 	    && ((headroom + tailroom) >= (4 + padlen))) {
 		if ((headroom < 4) || (tailroom < padlen)) {
 			skb->data = memmove(skb->head + 4, skb->data, skb->len);
-			skb->tail = skb->data + skb->len;
+			skb_set_tail_pointer(skb, skb->len);
 		}
 	} else {
 		struct sk_buff *skb2;
@@ -356,7 +356,7 @@ static struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 
 	if ((skb->len % 512) == 0) {
 		cpu_to_le32s(&padbytes);
-		memcpy( skb->tail, &padbytes, sizeof(padbytes));
+		memcpy(skb_tail_pointer(skb), &padbytes, sizeof(padbytes));
 		skb_put(skb, sizeof(padbytes));
 	}
 	return skb;
diff --git a/drivers/usb/net/gl620a.c b/drivers/usb/net/gl620a.c
index d257a8e026d..031cf5ca4db 100644
--- a/drivers/usb/net/gl620a.c
+++ b/drivers/usb/net/gl620a.c
@@ -157,7 +157,7 @@ genelink_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 		if ((headroom < (4 + 4*1)) || (tailroom < padlen)) {
 			skb->data = memmove(skb->head + (4 + 4*1),
 					     skb->data, skb->len);
-			skb->tail = skb->data + skb->len;
+			skb_set_tail_pointer(skb, skb->len);
 		}
 	} else {
 		struct sk_buff	*skb2;
diff --git a/drivers/usb/net/net1080.c b/drivers/usb/net/net1080.c
index ccebfdef475..19bf8dae70c 100644
--- a/drivers/usb/net/net1080.c
+++ b/drivers/usb/net/net1080.c
@@ -520,7 +520,7 @@ net1080_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 			skb->data = memmove(skb->head
 						+ sizeof (struct nc_header),
 					    skb->data, skb->len);
-			skb->tail = skb->data + len;
+			skb_set_tail_pointer(skb, len);
 			goto encapsulate;
 		}
 	}
diff --git a/drivers/usb/net/rndis_host.c b/drivers/usb/net/rndis_host.c
index 39a21c74fdf..1d36772ba6e 100644
--- a/drivers/usb/net/rndis_host.c
+++ b/drivers/usb/net/rndis_host.c
@@ -588,7 +588,7 @@ rndis_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 		if (likely((sizeof *hdr) <= room)) {
 			skb->data = memmove(skb->head + sizeof *hdr,
 					    skb->data, len);
-			skb->tail = skb->data + len;
+			skb_set_tail_pointer(skb, len);
 			goto fill;
 		}
 	}