On Fri, 4 Jun 2021 10:28:41 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> 在 2021/6/4 上午1:09, Xuan Zhuo 写道:
> > In virtio-net's large packet mode, there is a hole in the space behind
> > buf.
>
>
> before the buf actually or behind the vnet header?
>
>
> >
> > hdr_padded_len - hdr_len
> >
> > We must take this into account when calculating tailroom.
> >
> > [ 44.544385] skb_put.cold (net/core/skbuff.c:5254 (discriminator 1) net/core/skbuff.c:5252 (discriminator 1))
> > [ 44.544864] page_to_skb (drivers/net/virtio_net.c:485) [ 44.545361] receive_buf (drivers/net/virtio_net.c:849 drivers/net/virtio_net.c:1131)
> > [ 44.545870] ? netif_receive_skb_list_internal (net/core/dev.c:5714)
> > [ 44.546628] ? dev_gro_receive (net/core/dev.c:6103)
> > [ 44.547135] ? napi_complete_done (./include/linux/list.h:35 net/core/dev.c:5867 net/core/dev.c:5862 net/core/dev.c:6565)
> > [ 44.547672] virtnet_poll (drivers/net/virtio_net.c:1427 drivers/net/virtio_net.c:1525)
> > [ 44.548251] __napi_poll (net/core/dev.c:6985)
> > [ 44.548744] net_rx_action (net/core/dev.c:7054 net/core/dev.c:7139)
> > [ 44.549264] __do_softirq (./arch/x86/include/asm/jump_label.h:19 ./include/linux/jump_label.h:200 ./include/trace/events/irq.h:142 kernel/softirq.c:560)
> > [ 44.549762] irq_exit_rcu (kernel/softirq.c:433 kernel/softirq.c:637 kernel/softirq.c:649)
> > [ 44.551384] common_interrupt (arch/x86/kernel/irq.c:240 (discriminator 13))
> > [ 44.551991] ? asm_common_interrupt (./arch/x86/include/asm/idtentry.h:638)
> > [ 44.552654] asm_common_interrupt (./arch/x86/include/asm/idtentry.h:638)
> >
> > Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > Reported-by: Corentin Noël <corentin.noel@xxxxxxxxxxxxx>
> > Tested-by: Corentin Noël <corentin.noel@xxxxxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index fa407eb8b457..78a01c71a17c 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -406,7 +406,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> > * add_recvbuf_mergeable() + get_mergeable_buf_len()
> > */
> > truesize = headroom ? PAGE_SIZE : truesize;
> > - tailroom = truesize - len - headroom;
> > + tailroom = truesize - len - headroom - (hdr_padded_len - hdr_len);
>
>
> The patch looks correct and I saw it has been merged.
>
> But I prefer to do that in receive_big() instead of here.
>
> Thanks
How?
change truesize or headroom?
I didn't find a good way. Do you have a good way?
Thanks.
>
>
>
> > buf = p - headroom;
> >
> > len -= hdr_len;
>
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