net: Add skb_free_frag to replace use of put_page in freeing skb->head

This change adds a function called skb_free_frag which is meant to
compliment the function netdev_alloc_frag.  The general idea is to enable a
more lightweight version of page freeing since we don't actually need all
the overhead of a put_page, and we don't quite fit the model of __free_pages.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -2182,6 +2182,11 @@ static inline struct sk_buff *netdev_alloc_skb_ip_align(struct net_device *dev,
 	return __netdev_alloc_skb_ip_align(dev, length, GFP_ATOMIC);
 }
 
+static inline void skb_free_frag(void *addr)
+{
+	__free_page_frag(addr);
+}
+
 void *napi_alloc_frag(unsigned int fragsz);
 struct sk_buff *__napi_alloc_skb(struct napi_struct *napi,
 				 unsigned int length, gfp_t gfp_mask);

net/core/skbuff.c

@@ -436,7 +436,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 
 	skb = __build_skb(data, len);
 	if (unlikely(!skb)) {
-		put_page(virt_to_head_page(data));
+		skb_free_frag(data);
 		return NULL;
 	}
 
@@ -490,7 +490,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
 
 	skb = __build_skb(data, len);
 	if (unlikely(!skb)) {
-		put_page(virt_to_head_page(data));
+		skb_free_frag(data);
 		return NULL;
 	}
 
@@ -549,10 +549,12 @@ static void skb_clone_fraglist(struct sk_buff *skb)
 
 static void skb_free_head(struct sk_buff *skb)
 {
+	unsigned char *head = skb->head;
+
 	if (skb->head_frag)
-		put_page(virt_to_head_page(skb->head));
+		skb_free_frag(head);
 	else
-		kfree(skb->head);
+		kfree(head);
 }
 
 static void skb_release_data(struct sk_buff *skb)