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

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Date:   Mon, 6 Mar 2023 18:31:22 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Stefano Garzarella <sgarzare@...hat.com>
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 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? Just call 'virtio_transport_dec_rx_pkt(skb->len)'. skb
is never returned to queue to read it again, so i think may be there is no sense for
extra call 'skb_pull'?

Thanks, Arseniy
> 
> Thanks,
> Stefano
> 
>>
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 2e2a773df5c1..30b0539990ba 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -466,7 +466,6 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>>                     dequeued_len = err;
>>                 } else {
>>                     user_buf_len -= bytes_to_copy;
>> -                    skb_pull(skb, bytes_to_copy);
>>                 }
>>
>>                 spin_lock_bh(&vvs->rx_lock);
>> @@ -484,6 +483,7 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
>>                 msg->msg_flags |= MSG_EOR;
>>         }
>>
>> +        skb_pull(skb, skb->len);
>>         virtio_transport_dec_rx_pkt(vvs, skb);
>>         kfree_skb(skb);
>>     }
>> -- 
>> 2.25.1
>>
>