netdev - Re: [Patch net-next 4/5] net_sched: forbid setting default qdisc to inappropriate ones

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Message-Id: <20150827.212359.1624170801280596846.davem@davemloft.net>
Date:	Thu, 27 Aug 2015 21:23:59 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	xiyou.wangcong@...il.com
Cc:	netdev@...r.kernel.org, jhs@...atatu.com,
	stephen@...workplumber.org
Subject: Re: [Patch net-next 4/5] net_sched: forbid setting default qdisc
 to inappropriate ones

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Thu, 27 Aug 2015 18:49:09 -0700

> On Thu, Aug 27, 2015 at 4:18 PM, David Miller <davem@...emloft.net> wrote:
>> From: Cong Wang <xiyou.wangcong@...il.com>
>> Date: Thu, 27 Aug 2015 15:47:55 -0700
>>
>>> On Thu, Aug 27, 2015 at 3:42 PM, David Miller <davem@...emloft.net> wrote:
>>>> If you fix it properly, by making every qdisc capable of being ->init()'d
>>>> without explicit parameters, it will be the best behavior overall.
>>>
>>> The problem is ->init() is not even called when setting it as default,
>>> since setting a default qdisc doesn't need to create a qdisc. This is
>>> why the flag has to be in ops->flags rather than qdisc->flags.
>>
>> Just sounds like another shortcoming of how default qdiscs are handled,
> 
> It has to, due to its definition. I don't see any other way except we change
> the meaning of the default qdisc.

We are talking past eachother.

If a default qdisc like HTB is choosen, we invoke the ->init() function
and we change the HTB ->init() function to do something reasonable
if a NULL set of configuration attributes is given.  ie. make HTB use
some defaults.

Please explain to me why this won't fix the problem.
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