skb: Add inline helper for getting the skb end offset from head

With the recent changes for how we compute the skb truesize it occurs to me
we are probably going to have a lot of calls to skb_end_pointer -
skb->head.  Instead of running all over the place doing that it would make
more sense to just make it a separate inline skb_end_offset(skb) that way
we can return the correct value without having gcc having to do all the
optimization to cancel out skb->head - skb->head.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 21 insertions, 11 deletions

diff --git a/drivers/atm/ambassador.c b/drivers/atm/ambassador.c
index f8f41e0..89b30f3 100644
--- a/drivers/atm/ambassador.c
+++ b/drivers/atm/ambassador.c
@@ -802,7 +802,7 @@ static void fill_rx_pool (amb_dev * dev, unsigned char pool,
     }
     // cast needed as there is no %? for pointer differences
     PRINTD (DBG_SKB, "allocated skb at %p, head %p, area %li",
-	    skb, skb->head, (long) (skb_end_pointer(skb) - skb->head));
+	    skb, skb->head, (long) skb_end_offset(skb));
     rx.handle = virt_to_bus (skb);
     rx.host_address = cpu_to_be32 (virt_to_bus (skb->data));
     if (rx_give (dev, &rx, pool))
diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
index 1c05212..8974bd2 100644
--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -1258,7 +1258,7 @@ idt77252_rx_raw(struct idt77252_dev *card)
 	tail = readl(SAR_REG_RAWCT);
 
 	pci_dma_sync_single_for_cpu(card->pcidev, IDT77252_PRV_PADDR(queue),
-				    skb_end_pointer(queue) - queue->head - 16,
+				    skb_end_offset(queue) - 16,
 				    PCI_DMA_FROMDEVICE);
 
 	while (head != tail) {
diff --git a/drivers/net/wimax/i2400m/usb-rx.c b/drivers/net/wimax/i2400m/usb-rx.c
index e325768..b78ee67 100644
--- a/drivers/net/wimax/i2400m/usb-rx.c
+++ b/drivers/net/wimax/i2400m/usb-rx.c
@@ -277,7 +277,7 @@ retry:
 		d_printf(1, dev, "RX: size changed to %d, received %d, "
 			 "copied %d, capacity %ld\n",
 			 rx_size, read_size, rx_skb->len,
-			 (long) (skb_end_pointer(new_skb) - new_skb->head));
+			 (long) skb_end_offset(new_skb));
 		goto retry;
 	}
 		/* In most cases, it happens due to the hardware scheduling a
diff --git a/drivers/staging/octeon/ethernet-tx.c b/drivers/staging/octeon/ethernet-tx.c
index 56d74dc..418ed03 100644
--- a/drivers/staging/octeon/ethernet-tx.c
+++ b/drivers/staging/octeon/ethernet-tx.c
@@ -344,7 +344,7 @@ int cvm_oct_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 	if (unlikely
 	    (skb->truesize !=
-	     sizeof(*skb) + skb_end_pointer(skb) - skb->head)) {
+	     sizeof(*skb) + skb_end_offset(skb))) {
 		/*
 		   printk("TX buffer truesize has been changed\n");
 		 */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 37f5391..91ad5e2 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -645,11 +645,21 @@ static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 {
 	return skb->head + skb->end;
 }
+
+static inline unsigned int skb_end_offset(const struct sk_buff *skb)
+{
+	return skb->end;
+}
 #else
 static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
 {
 	return skb->end;
 }
+
+static inline unsigned int skb_end_offset(const struct sk_buff *skb)
+{
+	return skb->end - skb->head;
+}
 #endif
 
 /* Internal */
@@ -2558,7 +2568,7 @@ static inline bool skb_is_recycleable(const struct sk_buff *skb, int skb_size)
 		return false;
 
 	skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD);
-	if (skb_end_pointer(skb) - skb->head < skb_size)
+	if (skb_end_offset(skb) < skb_size)
 		return false;
 
 	if (skb_shared(skb) || skb_cloned(skb))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 17e4b1e..2c35da81 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -829,7 +829,7 @@ static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t gfp_mask)
 {
 	int headerlen = skb_headroom(skb);
-	unsigned int size = (skb_end_pointer(skb) - skb->head) + skb->data_len;
+	unsigned int size = skb_end_offset(skb) + skb->data_len;
 	struct sk_buff *n = alloc_skb(size, gfp_mask);
 
 	if (!n)
@@ -930,7 +930,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 {
 	int i;
 	u8 *data;
-	int size = nhead + (skb_end_pointer(skb) - skb->head) + ntail;
+	int size = nhead + skb_end_offset(skb) + ntail;
 	long off;
 
 	BUG_ON(nhead < 0);
@@ -2727,14 +2727,13 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
 			if (unlikely(!nskb))
 				goto err;
 
-			hsize = skb_end_pointer(nskb) - nskb->head;
+			hsize = skb_end_offset(nskb);
 			if (skb_cow_head(nskb, doffset + headroom)) {
 				kfree_skb(nskb);
 				goto err;
 			}
 
-			nskb->truesize += skb_end_pointer(nskb) - nskb->head -
-					  hsize;
+			nskb->truesize += skb_end_offset(nskb) - hsize;
 			skb_release_head_state(nskb);
 			__skb_push(nskb, doffset);
 		} else {
@@ -2883,7 +2882,8 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 		skb_frag_size_sub(frag, offset);
 
 		/* all fragments truesize : remove (head size + sk_buff) */
-		delta_truesize = skb->truesize - SKB_TRUESIZE(skb_end_pointer(skb) - skb->head);
+		delta_truesize = skb->truesize -
+				 SKB_TRUESIZE(skb_end_offset(skb));
 
 		skb->truesize -= skb->data_len;
 		skb->len -= skb->data_len;