On Wed, Nov 20, 2013 at 05:07:25PM +0800, Jason Wang wrote:
> When mergeable buffer were used, we only put the first page buf leave the rest
> of buffers in the virt queue. This will cause the driver could not get the
> correct head buffer any more. Fix this by dropping the rest of buffers for this
> packet.
>
> The bug was introduced by commit 9ab86bbcf8be755256f0a5e994e0b38af6b4d399
> (virtio_net: Defer skb allocation in receive path).
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Michael Dalton <mwdalton@xxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Shirley Ma <xma@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> This patch was needed for stable
> ---
> drivers/net/virtio_net.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7bab4de..24fd502 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -222,6 +222,17 @@ static void skb_xmit_done(struct virtqueue *vq)
> netif_wake_subqueue(vi->dev, vq2txq(vq));
> }
>
> +static void drop_mergeable_buffer(struct receive_queue *rq, int num_buf)
> +{
> + char *buf;
> + int len;
> +
> + while (--num_buf && (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> + --rq->num;
> + put_page(virt_to_head_page(buf));
> + }
> +}
> +
This is the same code we have in receive_mergeable anyway.
So let's reuse that.
> /* Called from bottom half context */
> static struct sk_buff *page_to_skb(struct receive_queue *rq,
> struct page *page, unsigned int offset,
> @@ -237,8 +248,13 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
>
> /* copy small packet so we can reuse these pages for small data */
> skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN);
> - if (unlikely(!skb))
> + if (unlikely(!skb)) {
> + if (vi->mergeable_rx_bufs) {
> + hdr = (struct skb_vnet_hdr *)p;
> + drop_mergeable_buffer(rq, hdr->mhdr.num_buffers);
> + }
> return NULL;
> + }
>
> hdr = skb_vnet_hdr(skb);
>
> --
> 1.8.3.2
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