sfc: Fix reading of inserted hash

The hash appears immediately before the packet data, not at the
beginning of the buffer. This means we can easily use negative offsets
from the start of packet data, so adjust the data and length at the
top of __efx_rx_packet() instead of wherever we consume the hash.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/sfc/rx.c b/drivers/net/sfc/rx.c
index 0fb9835..799c461 100644
--- a/drivers/net/sfc/rx.c
+++ b/drivers/net/sfc/rx.c
@@ -104,9 +104,9 @@
 static inline u32 efx_rx_buf_hash(struct efx_rx_buffer *buf)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) || NET_IP_ALIGN % 4 == 0
-	return __le32_to_cpup((const __le32 *)buf->data);
+	return __le32_to_cpup((const __le32 *)(buf->data - 4));
 #else
-	const u8 *data = (const u8 *)buf->data;
+	const u8 *data = (const u8 *)(buf->data - 4);
 	return ((u32)data[0]       |
 		(u32)data[1] << 8  |
 		(u32)data[2] << 16 |
@@ -469,8 +469,6 @@
 
 		if (efx->net_dev->features & NETIF_F_RXHASH)
 			skb->rxhash = efx_rx_buf_hash(rx_buf);
-		rx_buf->data += efx->type->rx_buffer_hash_size;
-		rx_buf->len -= efx->type->rx_buffer_hash_size;
 
 		skb_shinfo(skb)->frags[0].page = page;
 		skb_shinfo(skb)->frags[0].page_offset =
@@ -577,6 +575,9 @@
 	struct efx_nic *efx = channel->efx;
 	struct sk_buff *skb;
 
+	rx_buf->data += efx->type->rx_buffer_hash_size;
+	rx_buf->len -= efx->type->rx_buffer_hash_size;
+
 	/* If we're in loopback test, then pass the packet directly to the
 	 * loopback layer, and free the rx_buf here
 	 */
@@ -589,11 +590,11 @@
 	if (rx_buf->skb) {
 		prefetch(skb_shinfo(rx_buf->skb));
 
+		skb_reserve(rx_buf->skb, efx->type->rx_buffer_hash_size);
 		skb_put(rx_buf->skb, rx_buf->len);
 
 		if (efx->net_dev->features & NETIF_F_RXHASH)
 			rx_buf->skb->rxhash = efx_rx_buf_hash(rx_buf);
-		skb_pull(rx_buf->skb, efx->type->rx_buffer_hash_size);
 
 		/* Move past the ethernet header. rx_buf->data still points
 		 * at the ethernet header */
diff --git a/drivers/net/sfc/selftest.c b/drivers/net/sfc/selftest.c
index 0399be2..85f015f 100644
--- a/drivers/net/sfc/selftest.c
+++ b/drivers/net/sfc/selftest.c
@@ -258,9 +258,6 @@
 
 	payload = &state->payload;
 
-	buf_ptr += efx->type->rx_buffer_hash_size;
-	pkt_len -= efx->type->rx_buffer_hash_size;
-
 	received = (struct efx_loopback_payload *) buf_ptr;
 	received->ip.saddr = payload->ip.saddr;
 	if (state->offload_csum)