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

[Stefano Garzarella <sgarzare@redhat.com>]

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@kaspersky.com>
>---
> 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
>