[NETFILTER]: Avoid skb_copy/pskb_copy/skb_realloc_headroom

This patch replaces unnecessary uses of skb_copy, pskb_copy and
skb_realloc_headroom by functions such as skb_make_writable and
pskb_expand_head.

This allows us to remove the double pointers later.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 6ba98ac..3ceeffc 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -617,6 +617,7 @@
 nfqnl_mangle(void *data, int data_len, struct nfqnl_queue_entry *e)
 {
 	int diff;
+	int err;
 
 	diff = data_len - e->skb->len;
 	if (diff < 0) {
@@ -626,21 +627,14 @@
 		if (data_len > 0xFFFF)
 			return -EINVAL;
 		if (diff > skb_tailroom(e->skb)) {
-			struct sk_buff *newskb;
-
-			newskb = skb_copy_expand(e->skb,
-						 skb_headroom(e->skb),
-						 diff,
-						 GFP_ATOMIC);
-			if (newskb == NULL) {
+			err = pskb_expand_head(e->skb, 0,
+					       diff - skb_tailroom(e->skb),
+					       GFP_ATOMIC);
+			if (err) {
 				printk(KERN_WARNING "nf_queue: OOM "
 				      "in mangle, dropping packet\n");
-				return -ENOMEM;
+				return err;
 			}
-			if (e->skb->sk)
-				skb_set_owner_w(newskb, e->skb->sk);
-			kfree_skb(e->skb);
-			e->skb = newskb;
 		}
 		skb_put(e->skb, diff);
 	}