e1000: perform copybreak ahead of DMA unmap

Currently we unmap the DMA range, then copy to new skb.
Change this so we can keep the mapping in case the data is copied.
Signed-off-by: Florian Westphal <fw@strlen.de>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -4077,6 +4077,16 @@ static bool e1000_tbi_should_accept(struct e1000_adapter *adapter,
 	return false;
 }
 
+static struct sk_buff *e1000_alloc_rx_skb(struct e1000_adapter *adapter,
+					  unsigned int bufsz)
+{
+	struct sk_buff *skb = netdev_alloc_skb_ip_align(adapter->netdev, bufsz);
+
+	if (unlikely(!skb))
+		adapter->alloc_rx_buff_failed++;
+	return skb;
+}
+
 /**
  * e1000_clean_jumbo_rx_irq - Send received data up the network stack; legacy
  * @adapter: board private structure
@@ -4262,25 +4272,25 @@ static bool e1000_clean_jumbo_rx_irq(struct e1000_adapter *adapter,
 /* this should improve performance for small packets with large amounts
  * of reassembly being done in the stack
  */
-static void e1000_check_copybreak(struct net_device *netdev,
-				 struct e1000_buffer *buffer_info,
-				 u32 length, struct sk_buff **skb)
+static struct sk_buff *e1000_copybreak(struct e1000_adapter *adapter,
+				       struct e1000_buffer *buffer_info,
+				       u32 length, const void *data)
 {
-	struct sk_buff *new_skb;
+	struct sk_buff *skb;
 
 	if (length > copybreak)
-		return;
+		return NULL;
 
-	new_skb = netdev_alloc_skb_ip_align(netdev, length);
-	if (!new_skb)
-		return;
+	skb = e1000_alloc_rx_skb(adapter, length);
+	if (!skb)
+		return NULL;
+
+	dma_sync_single_for_cpu(&adapter->pdev->dev, buffer_info->dma,
+				length, DMA_FROM_DEVICE);
+
+	memcpy(skb_put(skb, length), data, length);
 
-	skb_copy_to_linear_data_offset(new_skb, -NET_IP_ALIGN,
-				       (*skb)->data - NET_IP_ALIGN,
-				       length + NET_IP_ALIGN);
-	/* save the skb in buffer_info as good */
-	buffer_info->skb = *skb;
-	*skb = new_skb;
+	return skb;
 }
 
 /**
@@ -4318,10 +4328,18 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 		rmb(); /* read descriptor and rx_buffer_info after status DD */
 
 		status = rx_desc->status;
-		skb = buffer_info->skb;
-		buffer_info->skb = NULL;
+		length = le16_to_cpu(rx_desc->length);
 
-		prefetch(skb->data - NET_IP_ALIGN);
+		prefetch(buffer_info->skb->data - NET_IP_ALIGN);
+		skb = e1000_copybreak(adapter, buffer_info, length,
+				      buffer_info->skb->data);
+		if (!skb) {
+			skb = buffer_info->skb;
+			buffer_info->skb = NULL;
+			dma_unmap_single(&pdev->dev, buffer_info->dma,
+					 buffer_info->length, DMA_FROM_DEVICE);
+			buffer_info->dma = 0;
+		}
 
 		if (++i == rx_ring->count) i = 0;
 		next_rxd = E1000_RX_DESC(*rx_ring, i);
@@ -4331,11 +4349,7 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 
 		cleaned = true;
 		cleaned_count++;
-		dma_unmap_single(&pdev->dev, buffer_info->dma,
-				 buffer_info->length, DMA_FROM_DEVICE);
-		buffer_info->dma = 0;
 
-		length = le16_to_cpu(rx_desc->length);
 		/* !EOP means multiple descriptors were used to store a single
 		 * packet, if thats the case we need to toss it.  In fact, we
 		 * to toss every packet with the EOP bit clear and the next
@@ -4348,8 +4362,7 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 		if (adapter->discarding) {
 			/* All receives must fit into a single buffer */
 			netdev_dbg(netdev, "Receive packet consumed multiple buffers\n");
-			/* recycle */
-			buffer_info->skb = skb;
+			dev_kfree_skb(skb);
 			if (status & E1000_RXD_STAT_EOP)
 				adapter->discarding = false;
 			goto next_desc;
@@ -4363,8 +4376,7 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 			} else if (netdev->features & NETIF_F_RXALL) {
 				goto process_skb;
 			} else {
-				/* recycle */
-				buffer_info->skb = skb;
+				dev_kfree_skb(skb);
 				goto next_desc;
 			}
 		}
@@ -4379,9 +4391,10 @@ static bool e1000_clean_rx_irq(struct e1000_adapter *adapter,
 			 */
 			length -= 4;
 
-		e1000_check_copybreak(netdev, buffer_info, length, &skb);
-
-		skb_put(skb, length);
+		if (buffer_info->skb == NULL)
+			skb_put(skb, length);
+		else /* copybreak skb */
+			skb_trim(skb, length);
 
 		/* Receive Checksum Offload */
 		e1000_rx_checksum(adapter,
@@ -4527,7 +4540,7 @@ static void e1000_alloc_rx_buffers(struct e1000_adapter *adapter,
 		skb = buffer_info->skb;
 		if (skb) {
 			skb_trim(skb, 0);
-			goto map_skb;
+			goto skip;
 		}
 
 		skb = netdev_alloc_skb_ip_align(netdev, bufsz);
@@ -4564,7 +4577,6 @@ static void e1000_alloc_rx_buffers(struct e1000_adapter *adapter,
 		}
 		buffer_info->skb = skb;
 		buffer_info->length = adapter->rx_buffer_len;
-map_skb:
 		buffer_info->dma = dma_map_single(&pdev->dev,
 						  skb->data,
 						  buffer_info->length,
@@ -4602,6 +4614,7 @@ static void e1000_alloc_rx_buffers(struct e1000_adapter *adapter,
 		rx_desc = E1000_RX_DESC(*rx_ring, i);
 		rx_desc->buffer_addr = cpu_to_le64(buffer_info->dma);
 
+skip:
 		if (unlikely(++i == rx_ring->count))
 			i = 0;
 		buffer_info = &rx_ring->buffer_info[i];