netdev - Re: [PATCH v2 net-next] net/sched: add skbprio scheduler

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Date:   Sat, 23 Jun 2018 14:43:16 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Nishanth Devarajan <ndev2021@...il.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cody Doucette <doucette@...edu>,
        Michel Machado <michel@...irati.com.br>
Subject: Re: [PATCH v2 net-next] net/sched: add skbprio scheduler

On Sat, Jun 23, 2018 at 1:47 PM, Nishanth Devarajan <ndev2021@...il.com> wrote:
> diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
> index 37b5096..6fd07e8 100644
> --- a/include/uapi/linux/pkt_sched.h
> +++ b/include/uapi/linux/pkt_sched.h
...
> +#define SKBPRIO_MAX_PRIORITY 64
> +
> +struct tc_skbprio_qopt {
> +       __u32   limit;          /* Queue length in packets. */
> +};


Since this is just an integer, you can just make it NLA_U32 instead
of a struct?


> +static int skbprio_change(struct Qdisc *sch, struct nlattr *opt,
> +                       struct netlink_ext_ack *extack)
> +{
> +       struct skbprio_sched_data *q = qdisc_priv(sch);
> +       struct tc_skbprio_qopt *ctl = nla_data(opt);
> +       const unsigned int min_limit = 1;
> +
> +       if (ctl->limit == (typeof(ctl->limit))-1)
> +               q->max_limit = max(qdisc_dev(sch)->tx_queue_len, min_limit);
> +       else if (ctl->limit < min_limit ||
> +               ctl->limit > qdisc_dev(sch)->tx_queue_len)
> +               return -EINVAL;
> +       else
> +               q->max_limit = ctl->limit;
> +
> +       return 0;
> +}

Isn't q->max_limit same with sch->limit?

Also, please avoid dev->tx_queue_len here, it may change
independently of your qdisc change, unless you want to implement
ops->change_tx_queue_len().