Re: [PATCH] vhost_net: revert upend_idx only on retriable error

[Jason Wang]

On Fri, Apr 21, 2023 at 3:04 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Thu, Dec 01, 2022 at 05:01:58PM +0800, Jason Wang wrote:
> > On Wed, Nov 23, 2022 at 6:24 PM Andrey Smetanin
> > <asmetanin@xxxxxxxxxxxxxx> wrote:
> > >
> > > Fix possible virtqueue used buffers leak and corresponding stuck
> > > in case of temporary -EIO from sendmsg() which is produced by
> > > tun driver while backend device is not up.
> > >
> > > In case of no-retriable error and zcopy do not revert upend_idx
> > > to pass packet data (that is update used_idx in corresponding
> > > vhost_zerocopy_signal_used()) as if packet data has been
> > > transferred successfully.
> >
> > Should we mark head.len as VHOST_DMA_DONE_LEN in this case?
> >
> > Thanks
>
> Jason do you want to take over this work? It's been stuck
> in my inbox for a while.

Andrey,

Any update on this patch?

Btw, if we haven't heard from Andrey for a week, I can do that.

Thanks

>
> > >
> > > Signed-off-by: Andrey Smetanin <asmetanin@xxxxxxxxxxxxxx>
> > > ---
> > >  drivers/vhost/net.c | 9 ++++++---
> > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > > index 20265393aee7..93e9166039b9 100644
> > > --- a/drivers/vhost/net.c
> > > +++ b/drivers/vhost/net.c
> > > @@ -934,13 +934,16 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> > >
> > >                 err = sock->ops->sendmsg(sock, &msg, len);
> > >                 if (unlikely(err < 0)) {
> > > +                       bool retry = err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS;
> > > +
> > >                         if (zcopy_used) {
> > >                                 if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)
> > >                                         vhost_net_ubuf_put(ubufs);
> > > -                               nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
> > > -                                       % UIO_MAXIOV;
> > > +                               if (retry)
> > > +                                       nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
> > > +                                               % UIO_MAXIOV;
> > >                         }
> > > -                       if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) {
> > > +                       if (retry) {
> > >                                 vhost_discard_vq_desc(vq, 1);
> > >                                 vhost_net_enable_vq(net, vq);
> > >                                 break;
> > > --
> > > 2.25.1
> > >
>