Re: [RFC PATCH v4 10/17] virtio/vsock: fetch length for SEQPACKET record

[Stefano Garzarella]

On Sun, Feb 07, 2021 at 06:17:08PM +0300, Arseny Krasnov wrote:
> This adds transport callback which tries to fetch record begin marker
> from socket's rx queue. It is called from af_vsock.c before reading data
> packets of record.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> ---
> include/linux/virtio_vsock.h            |  1 +
> net/vmw_vsock/virtio_transport_common.c | 40 +++++++++++++++++++++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index 4d0de3dee9a4..a5e8681bfc6a 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -85,6 +85,7 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> 			       struct msghdr *msg,
> 			       size_t len, int flags);
>
> +size_t virtio_transport_seqpacket_seq_get_len(struct vsock_sock *vsk);
> 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 4572d01c8ea5..7ac552bfd90b 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -420,6 +420,46 @@ static size_t virtio_transport_drop_until_seq_begin(struct virtio_vsock_sock *vv
> 	return bytes_dropped;
> }
>
> +size_t virtio_transport_seqpacket_seq_get_len(struct vsock_sock *vsk)
> +{
> +	struct virtio_vsock_seq_hdr *seq_hdr;
> +	struct virtio_vsock_sock *vvs;
> +	struct virtio_vsock_pkt *pkt;
> +	size_t bytes_dropped;
> +
> +	vvs = vsk->trans;
> +
> +	spin_lock_bh(&vvs->rx_lock);
> +
> +	/* Fetch all orphaned 'RW', packets, and
> +	 * send credit update.

Single line?

> +	 */
> +	bytes_dropped = virtio_transport_drop_until_seq_begin(vvs);
> +
> +	if (list_empty(&vvs->rx_queue))
> +		goto out;
> +
> +	pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
> +
> +	vvs->user_read_copied = 0;
> +
> +	seq_hdr = (struct virtio_vsock_seq_hdr *)pkt->buf;
> +	vvs->user_read_seq_len = le32_to_cpu(seq_hdr->msg_len);
> +	vvs->curr_rx_msg_cnt = le32_to_cpu(seq_hdr->msg_cnt);
> +	virtio_transport_dec_rx_pkt(vvs, pkt);
> +	virtio_transport_remove_pkt(pkt);
> +out:
> +	spin_unlock_bh(&vvs->rx_lock);
> +
> +	if (bytes_dropped)
> +		virtio_transport_send_credit_update(vsk,
> +						    VIRTIO_VSOCK_TYPE_SEQPACKET,
> +						    NULL);
> +
> +	return vvs->user_read_seq_len;
> +}
> +EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_seq_get_len);
> +
> static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
> 						 struct msghdr *msg,
> 						 bool *msg_ready)
> --
> 2.25.1