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

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Message-ID: <B25B4275-957C-4052-B089-3714B6A7B0A3@vmware.com>
Date:   Wed, 29 Mar 2023 21:44:56 +0000
From:   Vishnu Dasa <vdasa@...are.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>,
        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 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?

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.