On Tue, Nov 19, 2013 at 06:03:48AM -0800, Eric Dumazet wrote:
> On Tue, 2013-11-19 at 16:05 +0800, Jason Wang wrote:
> > We need to drop the refcnt of page when we fail to allocate an skb for frag
> > list, otherwise it will be leaked. The bug was introduced by commit
> > 2613af0ed18a11d5c566a81f9a6510b73180660a ("virtio_net: migrate mergeable rx
> > buffers to page frag allocators").
> >
> > Cc: Michael Dalton <mwdalton@xxxxxxxxxx>
> > Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> > Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > ---
> > The patch was needed for 3.12 stable.
>
> Good catch, but if we return from receive_mergeable() in the 'middle'
> of the frags we would need for the current skb, who will
> call the virtqueue_get_buf() to flush the remaining frags ?
>
> Don't we also need to call virtqueue_get_buf() like
>
> while (--num_buf) {
> buf = virtqueue_get_buf(rq->vq, &len);
> if (!buf)
> break;
> put_page(virt_to_head_page(buf));
> }
>
> ?
>
>
>
virtqueue_get_buf only gives you back a buffer that has been DMA-ed
to by hardware. ATM there's no way to get back a buffer once you
gave it to hardware without doing a NIC reset.
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