netdev - RE: Question: how to detect if a qdisc is root or not?

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Message-ID: <D5C1322C3E673F459512FB59E0DDC329034460BA@orsmsx414.amr.corp.intel.com>
Date:	Fri, 20 Jul 2007 15:59:25 -0700
From:	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
To:	"Patrick McHardy" <kaber@...sh.net>
Cc:	<netdev@...r.kernel.org>
Subject: RE: Question: how to detect if a qdisc is root or not?

> Its set after grafting the parent, which is after initialization.
> I think what should work is to set it in qdisc_create 
> instead, sch_api.c around line 490:
> 
> +	sch->parent = handle;
> 
>         if (handle == TC_H_INGRESS) {
>                 sch->flags |= TCQ_F_INGRESS;
>                 sch->stats_lock = &dev->ingress_lock; ...
> 
> and remove the initialization in qdisc_graft. That would 
> additionally have the benefit that ingress qdiscs also have 
> it initialized properly.

I just sent out a patch to fix this.  Sorry for the delay; my
development machine oops'd in the middle of some disk I/O, and it
corrupted part of the inode table...the ext3 journal application seemed
to make it worse too.  Rebuilt the machine, so I'm back on my feet.

Anyways, I tried a few different things, and what it looks like is
sch->parent will be NULL (0) for the top-level device.  This is correct,
and trying to mess with that screws up qdisc_graft() when unloading the
qdisc.  I also tried adding a TCQ_F_ROOT flag to sch->flags when classid
is TC_H_ROOT, but that also screwed up unloading the qdisc.

The ingress qdisc does have the parent handle set correctly, namely
NULL, since it will always be the top-level qdisc on ingress sessions.

Thx Patrick,
-PJ Waskiewicz
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