netdev - Re: Default qdisc not correctly initialized with custom MTU

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Date:   Mon, 9 Sep 2019 15:52:21 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Holger Hoffstätte <holger@...lied-asynchrony.com>
Cc:     Netdev <netdev@...r.kernel.org>
Subject: Re: Default qdisc not correctly initialized with custom MTU

On Mon, Sep 9, 2019 at 5:44 AM Holger Hoffstätte
<holger@...lied-asynchrony.com> wrote:
> I can't help but feel this is a slight bug in terms of initialization order,
> and that the default qdisc should only be created when it's first being
> used/attached to a link, not when the sysctls are configured.

Yeah, this is because the fq_codel qdisc is initialized once and
doesn't get any notification when the netdev's MTU get changed.
We can "fix" this by adding a NETDEV_CHANGEMTU notifier to
qdisc's, but I don't know if it is really worth the effort.

Is there any reason you can't change that order?

Thanks.