linux-kernel - Re: [RFC PATCH v1 2/3] virtio/vsock: use 'target' in notify_poll

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Message-ID: <20220720082307.djbf7qgnlsjmrxcf@sgarzare-redhat>
Date:   Wed, 20 Jul 2022 10:23:07 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>,
        Dexuan Cui <decui@...rosoft.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Krasnov Arseniy <oxffffaa@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>
Subject: Re: [RFC PATCH v1 2/3] virtio/vsock: use 'target' in notify_poll_in,
 callback.

On Wed, Jul 20, 2022 at 05:38:03AM +0000, Arseniy Krasnov wrote:
>On 19.07.2022 15:48, Stefano Garzarella wrote:
>> On Mon, Jul 18, 2022 at 08:17:31AM +0000, Arseniy Krasnov wrote:
>>> This callback controls setting of POLLIN,POLLRDNORM output bits
>>> of poll() syscall,but in some cases,it is incorrectly to set it,
>>> when socket has at least 1 bytes of available data. Use 'target'
>>> which is already exists and equal to sk_rcvlowat in this case.
>>>
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>>> ---
>>> net/vmw_vsock/virtio_transport_common.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>>> index ec2c2afbf0d0..591908740992 100644
>>> --- a/net/vmw_vsock/virtio_transport_common.c
>>> +++ b/net/vmw_vsock/virtio_transport_common.c
>>> @@ -634,7 +634,7 @@ virtio_transport_notify_poll_in(struct vsock_sock *vsk,
>>>                 size_t target,
>>>                 bool *data_ready_now)
>>> {
>>> -    if (vsock_stream_has_data(vsk))
>>> +    if (vsock_stream_has_data(vsk) >= target)
>>>         *data_ready_now = true;
>>>     else
>>>         *data_ready_now = false;
>>
>> Perhaps we can take the opportunity to clean up the code in this way:
>>
>>     *data_ready_now = vsock_stream_has_data(vsk) >= target;
>Ack
>>
>> Anyway, I think we also need to fix the other transports (vmci and hyperv), what do you think?
>For vmci it is look clear to fix it. For hyperv i need to check it more, because it already
>uses some internal target value.

Yep, I see. Maybe you can pass `target` to hvs_channel_readable() and 
use it as parameter of HVS_PKT_LEN().

@Dexuan what do you think?

Thanks,
Stefano