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@xxxxxxxxx>
> ---
> 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
