linux-kernel - Re: [RFC PATCH v4 06/17] vsock: check error queue to set EPOLLERR

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Message-ID: <pnbag2axu2uy7w2wrgiljutr3hifo3rltvkkc46wlrmhwzqr5b@pgaqr2m3iwof>
Date:   Tue, 27 Jun 2023 09:53:30 +0200
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>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...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 v4 06/17] vsock: check error queue to set EPOLLERR

On Tue, Jun 27, 2023 at 07:44:25AM +0300, Arseniy Krasnov wrote:
>
>
>On 26.06.2023 19:04, Stefano Garzarella wrote:
>> On Sat, Jun 03, 2023 at 11:49:28PM +0300, Arseniy Krasnov wrote:
>>> If socket's error queue is not empty, EPOLLERR must be set. Otherwise,
>>> reader of error queue won't detect data in it using EPOLLERR bit.
>>>
>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>>> ---
>>> net/vmw_vsock/af_vsock.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> This patch looks like it can go even without this series.
>>
>> Is it a fix? Should we add a fixes tag?
>
>Yes, it is fix and I can exclude it from this set to reduce number
>of patches, but there is no reproducer for this without MSG_ZEROCOPY
>support - at this moment this feature is the only user of error queue
>for AF_VSOCK.

Okay, so it's fine to keep it here, but please mention in the comment 
that without MSG_ZEROCOPY it can't be reproduced.

That way we know that we don't have to backport into the stable 
branches.

Thanks,
Stefano

>
>Thanks, Arseniy
>
>>
>> Thanks,
>> Stefano
>>
>>>
>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>> index efb8a0937a13..45fd20c4ed50 100644
>>> --- a/net/vmw_vsock/af_vsock.c
>>> +++ b/net/vmw_vsock/af_vsock.c
>>> @@ -1030,7 +1030,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
>>>     poll_wait(file, sk_sleep(sk), wait);
>>>     mask = 0;
>>>
>>> -    if (sk->sk_err)
>>> +    if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
>>>         /* Signify that there has been an error on this socket. */
>>>         mask |= EPOLLERR;
>>>
>>> -- 
>>> 2.25.1
>>>
>>
>