Re: [PATCH net 1/2] net/sched: pfifo_fast: cap ring size and account to memcg

[Jakub Kicinski <kuba@kernel.org>]

On Sat, 22 Aug 2026 18:14:49 -0400 Jamal Hadi Salim wrote:
> > On Thu, 20 Aug 2026 05:57:41 -0400 Jamal Hadi Salim wrote:  
> > > +     if (qlen > 65535) {
> > > +             pr_warn_ratelimited("pfifo_fast: capping ring size %u to 65535 for dev %s\n",
> > > +                                 qlen, qdisc_dev(qdisc)->name);
> > > +             qlen = 65535;
> > > +     }  
> >
> > Why not a hard cap?  
> 
> sorry, where to put the hard cap and what would it be?
> Or maybe you misspoke and intended to say "why put a hardcap"?
> 
> Or maybe in this case probably safer to just reject the change if > hard cap?

The latter, I'm asking why not:

if (qlen > 64k)
	return -EINVAL;

To be clear I didn't dig into the code, just read the commit msg, so
maybe you have a reason. But the "normal behavior" for out of range
params should be to return an error rather than silently clamp() into
the allowed range?