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

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Date:   Wed, 14 Sep 2016 07:33:27 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Cong Wang <xiyou.wangcong@...il.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 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.
I then tried another experiment and batch replaced several actions
including the one i know would fail. I placed the failing action in
the middle and hallelujah, all the actions before the middle one got
deleted.

So please ACK this so we can move forward.

cheers,
jamal