[PATCH 079/222] net:fec: make rx skb allocation/map more robust

[Russell King]

Allocate, and then map the receive skb before writing any data to the
ring descriptor or storing the skb.  This means we have ring data in
one of two states: either fully setup, or not setup.  This simplifies
the cleanup, which could end up calling dma_unmap_single() on a DMA
error value.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/net/ethernet/freescale/fec_main.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 45cb558bb227..f98ddb0923a3 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1712,12 +1712,11 @@ static void fec_enet_free_buffers(struct net_device *ndev)
 	bdp = fep->rx_bd_base;
 	for (i = 0; i < fep->rx_ring_size; i++) {
 		skb = fep->rx_skbuff[i];
-
-		if (bdp->cbd_bufaddr)
+		if (skb) {
 			dma_unmap_single(&fep->pdev->dev, bdp->cbd_bufaddr,
 					FEC_ENET_RX_FRSIZE, DMA_FROM_DEVICE);
-		if (skb)
 			dev_kfree_skb(skb);
+		}
 		bdp = fec_enet_get_nextdesc(bdp, fep);
 	}
 
@@ -1735,21 +1734,26 @@ static int fec_enet_alloc_buffers(struct net_device *ndev)
 
 	bdp = fep->rx_bd_base;
 	for (i = 0; i < fep->rx_ring_size; i++) {
+		dma_addr_t addr;
+
 		skb = netdev_alloc_skb(ndev, FEC_ENET_RX_FRSIZE);
 		if (!skb) {
 			fec_enet_free_buffers(ndev);
 			return -ENOMEM;
 		}
-		fep->rx_skbuff[i] = skb;
 
-		bdp->cbd_bufaddr = dma_map_single(&fep->pdev->dev, skb->data,
+		addr = dma_map_single(&fep->pdev->dev, skb->data,
 				FEC_ENET_RX_FRSIZE, DMA_FROM_DEVICE);
-		if (dma_mapping_error(&fep->pdev->dev, bdp->cbd_bufaddr)) {
+		if (dma_mapping_error(&fep->pdev->dev, addr)) {
+			dev_kfree_skb(skb);
 			fec_enet_free_buffers(ndev);
 			if (net_ratelimit())
 				netdev_err(ndev, "Rx DMA memory map failed\n");
 			return -ENOMEM;
 		}
+
+		fep->rx_skbuff[i] = skb;
+		bdp->cbd_bufaddr = addr;
 		bdp->cbd_sc = BD_ENET_RX_EMPTY;
 
 		if (fep->bufdesc_ex) {
-- 
1.8.3.1