net: add opaque struct around skb frag page

I've split this bit out of the skb frag destructor patch since it helps enforce
the use of the fragment API.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3411f22..94a23ff 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -140,7 +140,9 @@
 typedef struct skb_frag_struct skb_frag_t;
 
 struct skb_frag_struct {
-	struct page *page;
+	struct {
+		struct page *p;
+	} page;
 #if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
 	__u32 page_offset;
 	__u32 size;
@@ -1175,7 +1177,7 @@
 {
 	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
-	frag->page		  = page;
+	frag->page.p		  = page;
 	frag->page_offset	  = off;
 	skb_frag_size_set(frag, size);
 }
@@ -1699,7 +1701,7 @@
  */
 static inline struct page *skb_frag_page(const skb_frag_t *frag)
 {
-	return frag->page;
+	return frag->page.p;
 }
 
 /**
@@ -1785,7 +1787,7 @@
  */
 static inline void __skb_frag_set_page(skb_frag_t *frag, struct page *page)
 {
-	frag->page = page;
+	frag->page.p = page;
 }
 
 /**
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e271040..ca4db40 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -668,14 +668,14 @@
 
 	/* skb frags release userspace buffers */
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
-		put_page(skb_shinfo(skb)->frags[i].page);
+		skb_frag_unref(skb, i);
 
 	uarg->callback(uarg);
 
 	/* skb frags point to kernel buffers */
 	for (i = skb_shinfo(skb)->nr_frags; i > 0; i--) {
-		skb_shinfo(skb)->frags[i - 1].page_offset = 0;
-		skb_shinfo(skb)->frags[i - 1].page = head;
+		__skb_fill_page_desc(skb, i-1, head, 0,
+				     skb_shinfo(skb)->frags[i - 1].size);
 		head = (struct page *)head->private;
 	}