netdev - Re: [PATCH v3 net 1/1] net sched actions: fix GETing actions

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Message-ID: <CAM_iQpUgDVoZOkftuh1SyVWbJj_zK1vS7JF4oqfA=NpxCeH0_g@mail.gmail.com>
Date:   Wed, 14 Sep 2016 09:30:22 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 net 1/1] net sched actions: fix GETing actions

On Wed, Sep 14, 2016 at 4:33 AM, Jamal Hadi Salim <jhs@...atatu.com> wrote:
> On 16-09-13 03:47 PM, Jamal Hadi Salim wrote:
>>
>> On 16-09-13 12:20 PM, Cong Wang wrote:
>>>
>>> On Mon, Sep 12, 2016 at 4:07 PM, Jamal Hadi Salim <jhs@...atatu.com>
>>> wrote:
>
>
> [..]
>>>
>>> I am still trying to understand this piece, so here you hold the refcnt
>>> for the same action used by the later iteration? Otherwise there is
>>> almost none user inbetween hold and release...
>>>
>>> The comment you add is not clear to me, we use RTNL/RCU to
>>> sync destroy and replace, so how could that happen?
>>>
>>
>> I was worried about the destroy() hitting an error in that function.
>> If an action already existed and all we asked for was to
>> replace some attribute it would be deleted. It was the way the code was
>> before your changes so i just restored it to its original form.
>>
>
> And I have verified this is needed. I went and made gact return
> a failure if you replace something. I added a gact action; then
> when i replaced it failed. And when it failed it replace the existing
> action.

Oh, I see, the comments actually mislead me. ;) You are trying to
fix the rollback for failure path here... Makes sense to me now.

Thanks for verifying it.