Subject: Re: [PATCH 1b/2] tc: check for errors in gen_rate_estimator creation

From: Stephen Hemminger <[email-masked]>
Date: Tue, 25 Nov 2008 11:14:23 -0800

On Tue, 25 Nov 2008 20:05:46 +0100
Patrick McHardy <[email-masked]> wrote:

> Stephen Hemminger wrote:
> > The functions gen_new_estimator and gen_replace_estimator can return errors,
> > but they were being ignored.
> > 
> > Signed-off-by: Stephen Hemminger <[email-masked]>
> > 
> > 
> > ---
> > --- a/net/sched/sch_api.c	2008-11-25 10:51:47.000000000 -0800
> > +++ b/net/sched/sch_api.c	2008-11-25 10:54:16.000000000 -0800
> > @@ -887,6 +887,14 @@ static int qdisc_change(struct Qdisc *sc
> >  			return err;
> >  	}
> >  
> > +	if (tca[TCA_RATE]) {
> > +		err = gen_replace_estimator(&sch->bstats, &sch->rate_est,
> > +					    qdisc_root_sleeping_lock(sch),
> > +					    tca[TCA_RATE]);
> > +		if (err)
> > +			return err;
> 
> This appears to have the same problem as in HFSC unless I missed more
> code movement - changes to the qdisc have already been performed.

That is not fixable since both change and replace_estimator are non-unwindable,
and either one could fail. Could split checking and initialization out of gen_new_estimator,
but is it worth it??