linux-kernel - Re: [PATCH net-next 1/5] net/sched: taprio: don't overwrite "sch" variable in taprio_dump_class

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Date:   Tue, 30 May 2023 14:14:17 -0700
From:   Vinicius Costa Gomes <vinicius.gomes@...el.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Gerhard Engleder <gerhard@...leder-embedded.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Ferenc Fejes <ferenc.fejes@...csson.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Roger Quadros <rogerq@...nel.org>,
        Pranavi Somisetty <pranavi.somisetty@....com>,
        Harini Katakam <harini.katakam@....com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Michael Sit Wei Hong <michael.wei.hong.sit@...el.com>,
        Mohammad Athari Bin Ismail <mohammad.athari.ismail@...el.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Jacob Keller <jacob.e.keller@...el.com>,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        intel-wired-lan@...ts.osuosl.org,
        Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com>
Subject: Re: [PATCH net-next 1/5] net/sched: taprio: don't overwrite "sch"
 variable in taprio_dump_class_stats()

Hi,

Vladimir Oltean <vladimir.oltean@....com> writes:

> In taprio_dump_class_stats() we don't need a reference to the root Qdisc
> once we get the reference to the child corresponding to this traffic
> class, so it's okay to overwrite "sch". But in a future patch we will
> need the root Qdisc too, so create a dedicated "child" pointer variable
> to hold the child reference. This also makes the code adhere to a more
> conventional coding style.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---

The patch looks good:

Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>

But I have a suggestion, this "taprio_queue_get() ->
dev_queue->qdisc_sleeping()" dance should have the same result as
calling 'taprio_leaf()'.

I am thinking of using taprio_leaf() here and in taprio_dump_class().
Could be a separate commit.


>  net/sched/sch_taprio.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 76db9a10ef50..d29e6785854d 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -2388,10 +2388,10 @@ static int taprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
>  	__acquires(d->lock)
>  {
>  	struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);
> +	struct Qdisc *child = dev_queue->qdisc_sleeping;
>  
> -	sch = dev_queue->qdisc_sleeping;
> -	if (gnet_stats_copy_basic(d, NULL, &sch->bstats, true) < 0 ||
> -	    qdisc_qstats_copy(d, sch) < 0)
> +	if (gnet_stats_copy_basic(d, NULL, &child->bstats, true) < 0 ||
> +	    qdisc_qstats_copy(d, child) < 0)
>  		return -1;
>  	return 0;
>  }
> -- 
> 2.34.1
>

-- 
Vinicius