From: Alexander Kochetkov <al.koc...@gmail.com>
Date: Fri, 15 Dec 2017 20:20:06 +0300
> arc_emac_rx() has some issues found by code review.
>
> In case netdev_alloc_skb_ip_align() or dma_map_single() failure
> rx fifo entry will not be returned to EMAC.
>
> In case dma_map_single() failure previously allocated skb became
> lost to driver. At the same time address of newly allocated skb
> will not be provided to EMAC.
>
> Signed-off-by: Alexander Kochetkov <al.koc...@gmail.com>
This patch adds quite a few bugs, here is one which shows this is not
functionally tested:
> - /* receive_skb only if new skb was allocated to avoid holes */
> - netif_receive_skb(skb);
> -
> - addr = dma_map_single(&ndev->dev, (void *)rx_buff->skb->data,
> + addr = dma_map_single(&ndev->dev, (void *)skb->data,
> EMAC_BUFFER_SIZE, DMA_FROM_DEVICE);
Map the new SKB.
> if (dma_mapping_error(&ndev->dev, addr)) {
> if (net_ratelimit())
> - netdev_err(ndev, "cannot dma map\n");
> - dev_kfree_skb(rx_buff->skb);
> + netdev_err(ndev, "cannot map dma buffer\n");
> + dev_kfree_skb(skb);
> + /* Return ownership to EMAC */
> + rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
> stats->rx_errors++;
> + stats->rx_dropped++;
> continue;
> }
> +
> + /* unmap previosly mapped skb */
> + dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
> + dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);
And then you unmap it. "addr" is the new DMA mapping, not the old one.
