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

[Stefano Garzarella <sgarzare@redhat.com>]

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@kaspersky.com>
>---
> 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