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Date:   Sat, 16 Nov 2019 12:42:33 -0800 (PST)
Message-Id: <20191116.124233.2034551092704813586.davem@davemloft.net>
To:     ivan.khoronzhuk@linaro.org
Cc:     netdev@vger.kernel.org, vinicius.gomes@intel.com, jhs@mojatatu.com,
        xiyou.wangcong@gmail.com, jiri@resnulli.us,
        linux-kernel@vger.kernel.org
Subject: Re: [net-next PATCH] taprio: don't reject same mqprio settings
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20191115015607.11291-1-ivan.khoronzhuk@linaro.org>
References: <20191115015607.11291-1-ivan.khoronzhuk@linaro.org>
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From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Date: Fri, 15 Nov 2019 03:56:07 +0200

> @@ -1347,6 +1347,26 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb,
>  	return err;
>  }
>  
> +static int taprio_mqprio_cmp(struct net_device *dev,
> +			     struct tc_mqprio_qopt *mqprio)
> +{
 ...
>  static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
>  			 struct netlink_ext_ack *extack)
>  {
> @@ -1398,6 +1418,10 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
>  	admin = rcu_dereference(q->admin_sched);
>  	rcu_read_unlock();
>  
> +	/* no changes - no new mqprio settings */
> +	if (mqprio && !taprio_mqprio_cmp(dev, mqprio))
> +		mqprio = NULL;
> +

I like Vinicius's feedback, please make the new helper function have
the signature:

static int taprio_mqprio_cmp(const struct net_device *dev,
			     const struct tc_mqprio_qopt *mqprio)

And make the NULL check in there instead of at the caller.

Please also remember to add the Fixes: tag.

Thanks.