linux-kernel - Re: [PATCH net-next v3] net: sched: gred: dynamically allocate tc_gred_qopt

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Date:   Tue, 26 Oct 2021 13:43:51 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Denis Kirjanov <dkirjanov@...e.de>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Zheng Yongjun <zhengyongjun3@...wei.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net-next v3] net: sched: gred: dynamically allocate
 tc_gred_qopt_offload

On 2021-10-26 14:16:16 [+0300], Denis Kirjanov wrote:
> 10/26/21 1:51 PM, Sebastian Andrzej Siewior пишет:
> > On 2021-10-26 13:42:24 [+0300], Denis Kirjanov wrote:
> > > > diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
> > > > index 72de08ef8335e..1073c76d05c45 100644
> > > > --- a/net/sched/sch_gred.c
> > > > +++ b/net/sched/sch_gred.c
> > > > @@ -311,42 +312,43 @@ static void gred_offload(struct Qdisc *sch, enum tc_gred_command command)
> > > >    {
> > > >    	struct gred_sched *table = qdisc_priv(sch);
> > > >    	struct net_device *dev = qdisc_dev(sch);
> > > > -	struct tc_gred_qopt_offload opt = {
> > > > -		.command	= command,
> > > > -		.handle		= sch->handle,
> > > > -		.parent		= sch->parent,
> > > > -	};
> > > > +	struct tc_gred_qopt_offload *opt = table->opt;
> > > >    	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
> > > >    		return;
> > > > +	memset(opt, 0, sizeof(*opt));
> > > 
> > > It's zeroed in kzalloc()
> > 
> > but it is not limited to a single invocation?
> 
> I meant that all fields are set in the function as it was with the stack
> storage.

What about?
|                for (i = 0; i < table->DPs; i++) {
|                        struct gred_sched_data *q = table->tab[i];
| 
|                        if (!q)
|                                continue;

The stack storage version has an implicit memset().

Sebastian