netdev - 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
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 <michael.wei.hong.sit@...el.com>, Mohammad Athari Bin Ismail
 <mohammad.athari.ismail@...el.com>, Oleksij Rempel
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 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