Date:   Mon, 20 Mar 2023 16:07:15 +0100
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Arseniy Krasnov <avkrasnov@sberdevices.ru>
Cc:     Stefan Hajnoczi <stefanha@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel@sberdevices.ru, oxffffaa@gmail.com
Subject: Re: [RFC PATCH v1 2/3] virtio/vsock: add WARN() for invalid state of
 socket
Message-ID: <20230320150715.twapgesp2gj6egua@sgarzare-redhat>
References: <e141e6f1-00ae-232c-b840-b146bdb10e99@sberdevices.ru>
 <da93402d-920e-c248-a5a1-baf24b70ebee@sberdevices.ru>
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In-Reply-To: <da93402d-920e-c248-a5a1-baf24b70ebee@sberdevices.ru>
Precedence: bulk

On Sun, Mar 19, 2023 at 09:52:19PM +0300, Arseniy Krasnov wrote:
>This prints WARN() and returns from stream dequeue callback when socket's
>queue is empty, but 'rx_bytes' still non-zero.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 3c75986e16c2..c35b03adad8d 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -388,6 +388,13 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> 	u32 free_space;
>
> 	spin_lock_bh(&vvs->rx_lock);
>+
>+	if (skb_queue_empty(&vvs->rx_queue) && vvs->rx_bytes) {
>+		WARN(1, "No skbuffs with non-zero 'rx_bytes'\n");

I would use WARN_ONCE, since we can't recover so we will flood the log.

And you can put the condition in the first argument, I mean something
like this:
         if (WARN_ONCE(skb_queue_empty(&vvs->rx_queue) && vvs->rx_bytes,
                       "rx_queue is empty, but rx_bytes is non-zero\n")) {

Thanks,
Stefano

>+		spin_unlock_bh(&vvs->rx_lock);
>+		return err;
>+	}
>+
> 	while (total < len && !skb_queue_empty(&vvs->rx_queue)) {
> 		skb = skb_peek(&vvs->rx_queue);
>
>-- 
>2.25.1
>