virtio_net: small: remove the delta

In the case of XDP-PASS, skb_reserve uses the "delta" to compatible
non-XDP, now that is not shared between xdp and non-xdp, so we can
remove this logic.
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/virtio_net.c

@@ -949,9 +949,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	unsigned int buflen;
 	struct xdp_buff xdp;
 	struct sk_buff *skb;
-	unsigned int delta = 0;
 	unsigned int metasize = 0;
-	void *orig_data;
 	u32 act;
 
 	if (unlikely(hdr->hdr.gso_type))
@@ -984,14 +982,12 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
 	xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
 			 xdp_headroom, len, true);
-	orig_data = xdp.data;
 
 	act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
 
 	switch (act) {
 	case XDP_PASS:
 		/* Recalculate length in case bpf program changed it */
-		delta = orig_data - xdp.data;
 		len = xdp.data_end - xdp.data;
 		metasize = xdp.data - xdp.data_meta;
 		break;
@@ -1008,7 +1004,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	if (!skb)
 		goto err;
 
-	skb_reserve(skb, headroom - delta);
+	skb_reserve(skb, xdp.data - buf);
 	skb_put(skb, len);
 	if (metasize)
 		skb_metadata_set(skb, metasize);