virtio/vsock: check SO_RCVLOWAT before wake up reader

This adds extra condition to wake up data reader: do it only when number
of readable bytes >= SO_RCVLOWAT. Otherwise, there is no sense to kick
user,because it will wait until SO_RCVLOWAT bytes will be dequeued. This
check is performed in vsock_data_ready().

Signed-off-by: Arseniy Krasnov <[e-mail]>
Reviewed-by: Stefano Garzarella <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

net/vmw_vsock/virtio_transport_common.c

···
 	switch (le16_to_cpu(pkt->hdr.op)) {
 	case VIRTIO_VSOCK_OP_RW:
 		virtio_transport_recv_enqueue(vsk, pkt);
-		sk->sk_data_ready(sk);
+		vsock_data_ready(sk);
 		return err;
 	case VIRTIO_VSOCK_OP_CREDIT_REQUEST:
 		virtio_transport_send_credit_update(vsk);