netdev - Re: [RFC PATCH v2 2/4] virtio/vsock: remove all data from sk

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Message-ID: <20230306155121.7xwxzgxtle7qjbnc@sgarzare-redhat>
Date:   Mon, 6 Mar 2023 16:51:21 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v2 2/4] virtio/vsock: remove all data from sk_buff

On Mon, Mar 06, 2023 at 06:31:22PM +0300, Arseniy Krasnov wrote:
>
>
>On 06.03.2023 15:08, Stefano Garzarella wrote:
>> On Sun, Mar 05, 2023 at 11:07:37PM +0300, Arseniy Krasnov wrote:
>>> In case of SOCK_SEQPACKET all sk_buffs are used once - after read some
>>> data from it, it will be removed, so user will never read rest of the
>>> data. Thus we need to update credit parameters of the socket like whole
>>> sk_buff is read - so call 'skb_pull()' for the whole buffer.
>>>
>>> Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>>> ---
>>> net/vmw_vsock/virtio_transport_common.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> Maybe we could avoid this patch if we directly use pkt_len as I
>> suggested in the previous patch.
>Hm, may be we can avoid calling 'skb_pull()' here if 'virtio_transport_dec_rx_pkt()'
>will use integer argument?

Yep, exactly!

>Just call 'virtio_transport_dec_rx_pkt(skb->len)'. skb

It depends on how we call virtio_transport_inc_rx_pkt(). If we use
hdr->len there I would use the same to avoid confusion. Plus that's the
value the other peer sent us, so definitely the right value to increase
fwd_cnt with. But if skb->len always reflects it, then that's fine.

>is never returned to queue to read it again, so i think may be there is no sense for
>extra call 'skb_pull'?

Right!

Thanks,
Stefano