Re: [RFC PATCH v9 11/19] virtio/vsock: dequeue callback for SOCK_SEQPACKET

[Stefano Garzarella]

On Sat, May 08, 2021 at 07:35:20PM +0300, Arseny Krasnov wrote:
> This adds transport callback and it's logic for SEQPACKET dequeue.
> Callback fetches RW packets from rx queue of socket until whole record
> is copied(if user's buffer is full, user is not woken up). This is done
> to not stall sender, because if we wake up user and it leaves syscall,
> nobody will send credit update for rest of record, and sender will wait
> for next enter of read syscall at receiver's side. So if user buffer is
> full, we just send credit update and drop data.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> ---
> v8 -> v9:
> 1) Check for RW packet type is removed from loop(all packet now
>    considered RW).
> 2) Locking in loop is fixed.
> 3) cpu_to_le32()/le32_to_cpu() now used.
> 4) MSG_TRUNC handling removed from transport.
>
> include/linux/virtio_vsock.h            |  5 ++
> net/vmw_vsock/virtio_transport_common.c | 64 +++++++++++++++++++++++++
> 2 files changed, 69 insertions(+)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index dc636b727179..02acf6e9ae04 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -80,6 +80,11 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> 			       struct msghdr *msg,
> 			       size_t len, int flags);
>
> +ssize_t
> +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
> +				   struct msghdr *msg,
> +				   int flags,
> +				   bool *msg_ready);
> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
> s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index ad0d34d41444..f649a21dd23b 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -393,6 +393,58 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> 	return err;
> }
>
> +static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
> +						 struct msghdr *msg,
> +						 int flags,
> +						 bool *msg_ready)
> +{
> +	struct virtio_vsock_sock *vvs = vsk->trans;
> +	struct virtio_vsock_pkt *pkt;
> +	int err = 0;
> +	size_t user_buf_len = msg->msg_iter.count;

Forgot to mention that also here is better to use `msg_data_left(msg)`

Thanks,
Stefano