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

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Date:   Tue, 28 Mar 2023 13:19:13 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>,
        Vishnu Dasa <vdasa@...are.com>
Cc:     Bryan Tan <bryantan@...are.com>,
        VMware PV-Drivers Reviewers <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, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v1 1/2] vsock: return errors other than -ENOMEM to
 socket

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://www.spinics.net/lists/kernel/msg4611091.html
>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_*?

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
>>>>
>>
>