netdev - Re: [PATCH 3/4] vsock: add pkt cancel capability

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Date:   Wed, 7 Dec 2016 13:22:06 +0000
From:   Stefan Hajnoczi <stefanha@...il.com>
To:     Peng Tao <bergwolf@...il.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH 3/4] vsock: add pkt cancel capability

On Wed, Dec 07, 2016 at 06:00:20PM +0800, Peng Tao wrote:
> Signed-off-by: Peng Tao <bergwolf@...il.com>
> ---
>  net/vmw_vsock/virtio_transport.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index 936d7ee..f88b6ed 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -170,6 +170,41 @@ virtio_transport_send_pkt(struct virtio_vsock_pkt *pkt)
>  	return len;
>  }
>  
> +static int
> +virtio_transport_cancel_pkt(struct vsock_sock *vsk)
> +{
> +	struct virtio_vsock *vsock;
> +	struct virtio_vsock_pkt *pkt, *n;
> +	int cnt = 0;
> +	LIST_HEAD(freeme);
> +
> +	vsock = virtio_vsock_get();
> +	if (!vsock) {
> +		return -ENODEV;
> +	}
> +
> +	if (pkt->reply)

pkt is uninitialized.  I guess this if statement should be deleted, you
already take care of counting reply packets below.

> +		cnt++;
> +
> +	spin_lock_bh(&vsock->send_pkt_list_lock);
> +	list_for_each_entry_safe(pkt, n, &vsock->send_pkt_list, list) {
> +		if (pkt->vsk != vsk)
> +			continue;
> +		list_move(&pkt->list, &freeme);
> +	}
> +	spin_unlock_bh(&vsock->send_pkt_list_lock);
> +
> +	list_for_each_entry_safe(pkt, n, &freeme, list) {
> +		if (pkt->reply)
> +			cnt++;
> +		list_del(&pkt->list);
> +		virtio_transport_free_pkt(pkt);
> +	}
> +	atomic_sub(cnt, &vsock->queued_replies);

If we stopped rx because there were too many replies in flight then we
might be able to resume rx now:

/* Do we now have resources to resume rx processing? */
if (old_val >= virtqueue_get_vring_size(rx_vq) &&
    new_val < virtqueue_get_vring_size(rx_vq))
	queue_work(virtio_vsock_workqueue, &vsock->rx_work);

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