linux-kernel - Re: [RFC PATCH v1 1/2] vsock: return errors other than -ENOMEM to socket

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Message-ID: <3083bb71-45bd-0738-14b6-fe2860c61b09@sberdevices.ru>
Date:   Thu, 30 Mar 2023 08:13:12 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Vishnu Dasa <vdasa@...are.com>,
        Stefano Garzarella <sgarzare@...hat.com>
CC:     Bryan Tan <bryantan@...are.com>,
        Pv-drivers <Pv-drivers@...are.com>,
        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" <kvm@...r.kernel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        Krasnov Arseniy <oxffffaa@...il.com>
Subject: Re: [RFC PATCH v1 1/2] vsock: return errors other than -ENOMEM to
 socket



On 30.03.2023 00:44, Vishnu Dasa wrote:
> 
> 
>> On Mar 28, 2023, at 4:20 AM, Arseniy Krasnov <AVKrasnov@...rdevices.ru> wrote:
>>
>> !! External Email
>>
>> On 28.03.2023 14:19, Stefano Garzarella wrote:
>>> On Tue, Mar 28, 2023 at 01:42:19PM +0300, Arseniy Krasnov wrote:
>>>>
>>>>
>>>> On 28.03.2023 12:42, Stefano Garzarella wrote:
>>>>> I pressed send too early...
>>>>>
>>>>> CCing Bryan, Vishnu, and pv-drivers@...are.com
>>>>>
>>>>> On Tue, Mar 28, 2023 at 11:39 AM Stefano Garzarella <sgarzare@...hat.com> wrote:
>>>>>>
>>>>>> On Sun, Mar 26, 2023 at 01:13:11AM +0300, Arseniy Krasnov wrote:
>>>>>>> This removes behaviour, where error code returned from any transport
>>>>>>> was always switched to ENOMEM. This works in the same way as:
>>>>>>> commit
>>>>>>> c43170b7e157 ("vsock: return errors other than -ENOMEM to socket"),
>>>>>>> but for receive calls.
>>>>>>>
>>>>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>>>>>>> ---
>>>>>>> net/vmw_vsock/af_vsock.c | 4 ++--
>>>>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>>>>>> index 19aea7cba26e..9262e0b77d47 100644
>>>>>>> --- a/net/vmw_vsock/af_vsock.c
>>>>>>> +++ b/net/vmw_vsock/af_vsock.c
>>>>>>> @@ -2007,7 +2007,7 @@ static int __vsock_stream_recvmsg(struct sock *sk, struct msghdr *msg,
>>>>>>>
>>>>>>>              read = transport->stream_dequeue(vsk, msg, len - copied, flags);
>>>>>>
>>>>>> In vmci_transport_stream_dequeue() vmci_qpair_peekv() and
>>>>>> vmci_qpair_dequev() return VMCI_ERROR_* in case of errors.
>>>>>>
>>>>>> Maybe we should return -ENOMEM in vmci_transport_stream_dequeue() if
>>>>>> those functions fail to keep the same behavior.
>>>>
>>>> Yes, seems i missed it, because several months ago we had similar question for send
>>>> logic:
>>>> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Fkernel%2Fmsg4611091.html&data=05%7C01%7Cvdasa%40vmware.com%7C3b17793425384debe75708db2f7eec8c%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C638155994413494900%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=MMfFcKuFFvMcJrbToKvWvIB%2FZmzp%2BdGGVWFVWztuSzg%3D&reserved=0
>>>> And it was ok to not handle VMCI send path in this way. So i think current implementation
>>>> for tx is a little bit buggy, because VMCI specific error from 'vmci_qpair_enquev()' is
>>>> returned to af_vsock.c. I think error conversion must be added to VMCI transport for tx
>>>> also.
>>>
>>> Good point!
>>>
>>> These are negative values, so there are no big problems, but I don't
>>> know what the user expects in this case.
>>>
>>> @Vishnu Do we want to return an errno to the user or a VMCI_ERROR_*?
>>
>> Small remark, as i can see, VMCI_ERROR_ is not exported to user in include/uapi,
>> so IIUC user won't be able to interpret such values correctly.
>>
>> Thanks, Arseniy
> 
> Let's just return -ENOMEM from vmci transport in case of error in
> vmci_transport_stream_enqueue and vmci_transport_stream_dequeue.
> 
> @Arseniy,
> Could you please add a separate patch in this set to handle the above?

Sure, ack, in the next few days!

Thanks, Arseniy

> 
> Thanks,
> Vishnu
> 
>>
>>>
>>> In both cases I think we should do the same for both enqueue and
>>> dequeue.
>>>
>>>>
>>>> Good thing is that Hyper-V uses general error codes.
>>>
>>> Yeah!
>>>
>>> Thanks,
>>> Stefano
>>>
>>>>
>>>> Thanks, Arseniy
>>>>>>
>>>>>> CCing Bryan, Vishnu, and pv-drivers@...are.com
>>>>>>
>>>>>> The other transports seem okay to me.
>>>>>>
>>>>>> Thanks,
>>>>>> Stefano
>>>>>>
>>>>>>>              if (read < 0) {
>>>>>>> -                      err = -ENOMEM;
>>>>>>> +                      err = read;
>>>>>>>                      break;
>>>>>>>              }
>>>>>>>
>>>>>>> @@ -2058,7 +2058,7 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
>>>>>>>      msg_len = transport->seqpacket_dequeue(vsk, msg, flags);
>>>>>>>
>>>>>>>      if (msg_len < 0) {
>>>>>>> -              err = -ENOMEM;
>>>>>>> +              err = msg_len;
>>>>>>>              goto out;
>>>>>>>      }
>>>>>>>
>>>>>>> --
>>>>>>> 2.25.1
>>>>>>>
>>>>>
>>>>
>>>
>>
>> !! External Email: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender.
> 
>