On Wed, Nov 20, 2013 at 07:08:02AM -0500, Jason Wang wrote:
>
>
> ----- 原始邮件 -----
> > 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.
> >
> >
>
> receive_mergeable() was called after page_to_skb() was called and
> there's lots of conditions check there. I'm not sure how could we
> reuse them.
I posted a patch showing how :)
> > > /* 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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