On Mon, Sep 23, 2019 at 09:58:30AM +0200, Stefano Garzarella
wrote:> Hi Matias,
> thanks for this patch!
>
> Since this patch only concerns virtio_transport,
> I'd use the 'vsock/virtio' prefix in the commit title:
> "vsock/virtio: add support for MSG_PEEK"
>
> Some comments below:
>
> On Sun, Sep 22, 2019 at 05:48:27PM +0000, Matias Ezequiel Vara Larsen
wrote:
> > This patch adds support for MSG_PEEK. In such a case, packets are not
> > removed from the rx_queue and credit updates are not sent.
> >
> > Signed-off-by: Matias Ezequiel Vara Larsen <matiasevara at
gmail.com>
> > ---
> > net/vmw_vsock/virtio_transport_common.c | 59
+++++++++++++++++++++++++++++++--
> > 1 file changed, 56 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/vmw_vsock/virtio_transport_common.c
b/net/vmw_vsock/virtio_transport_common.c
> > index 94cc0fa..830e890 100644
> > --- a/net/vmw_vsock/virtio_transport_common.c
> > +++ b/net/vmw_vsock/virtio_transport_common.c
> > @@ -264,6 +264,59 @@ static int
virtio_transport_send_credit_update(struct vsock_sock *vsk,
> > }
> >
> > static ssize_t
> > +virtio_transport_stream_do_peek(struct vsock_sock *vsk,
> > + struct msghdr *msg,
> > + size_t len)
> > +{
> > + struct virtio_vsock_sock *vvs = vsk->trans;
> > + struct virtio_vsock_pkt *pkt;
> > + size_t bytes, off = 0, total = 0;
> > + int err = -EFAULT;
> > +
> > + spin_lock_bh(&vvs->rx_lock);
> > +
>
> What about using list_for_each_entry() to cycle through the queued packets?
>
> > + if (list_empty(&vvs->rx_queue)) {
> > + spin_unlock_bh(&vvs->rx_lock);
> > + return 0;
> > + }
> > +
> > + pkt = list_first_entry(&vvs->rx_queue,
> > + struct virtio_vsock_pkt, list);
> > + do {
>
> pkt->off contains the offset inside the packet where the unread data
starts.
> So here we should initialize 'off':
>
> off = pkt->off;
>
> Or just use pkt->off later (without increasing it as in the dequeue).
>
> > + bytes = len - total;
> > + if (bytes > pkt->len - off)
> > + bytes = pkt->len - off;
> > +
> > + /* sk_lock is held by caller so no one else can dequeue.
> > + * Unlock rx_lock since memcpy_to_msg() may sleep.
> > + */
> > + spin_unlock_bh(&vvs->rx_lock);
> > +
> > + err = memcpy_to_msg(msg, pkt->buf + off, bytes);
> > + if (err)
> > + goto out;
> > +
> > + spin_lock_bh(&vvs->rx_lock);
> > +
> > + total += bytes;
>
> Using list_for_each_entry(), here we can just do:
> (or better, at the beginning of the cycle)
>
> if (total == len)
> break;
>
> removing the next part...
>
> > + off += bytes;
> > + if (off == pkt->len) {
> > + pkt = list_next_entry(pkt, list);
> > + off = 0;
> > + }
> > + } while ((total < len) &&
!list_is_first(&pkt->list, &vvs->rx_queue));
>
> ...until here.
>
> > +
> > + spin_unlock_bh(&vvs->rx_lock);
> > +
> > + return total;
> > +
> > +out:
> > + if (total)
> > + err = total;
> > + return err;
> > +}
> > +
> > +static ssize_t
> > virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> > struct msghdr *msg,
> > size_t len)
> > @@ -330,9 +383,9 @@ virtio_transport_stream_dequeue(struct vsock_sock
*vsk,
> > size_t len, int flags)
> > {
> > if (flags & MSG_PEEK)
> > - return -EOPNOTSUPP;
> > -
> > - return virtio_transport_stream_do_dequeue(vsk, msg, len);
> > + return virtio_transport_stream_do_peek(vsk, msg, len);
> > + else
> > + return virtio_transport_stream_do_dequeue(vsk, msg, len);
> > }
> > EXPORT_SYMBOL_GPL(virtio_transport_stream_dequeue);
> >
>
> The rest looks good to me!
>
> Thanks,
> Stefano
Thanks Stefano. Based on your comments, I will modify the patch and
resubmit it.
Matias