linux-kernel - Re: [PATCH] net: cls_api: remove unneeded local variable in tc_dump

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Message-ID: <CAM_iQpUfE2f3QBFY6r0_D2mzFK_SsmFXdA-1p3h7yquM8912fg@mail.gmail.com>
Date:   Wed, 28 Oct 2020 10:38:45 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Tom Rix <trix@...hat.com>
Cc:     Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org, linux-safety@...ts.elisa.tech
Subject: Re: [PATCH] net: cls_api: remove unneeded local variable in tc_dump_chain()

On Wed, Oct 28, 2020 at 6:59 AM Tom Rix <trix@...hat.com> wrote:
>
>
> On 10/28/20 4:35 AM, Lukas Bulwahn wrote:
> > @@ -2971,13 +2963,11 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
> >               if (!dev)
> >                       return skb->len;
> >
> > -             parent = tcm->tcm_parent;
> > -             if (!parent) {
> > +             if (!tcm->tcm_parent)
> >                       q = dev->qdisc;
> > -                     parent = q->handle;
>
> This looks like a an unused error handler.
>
> and the later call to
>
> if (TC_H_MIN(tcm->tcm_parent)
>
> maybe should be
>
> if (TC_H_MIN(parent))

When tcm->tcm_parent is 0, TC_H_MIN(tcm->tcm_parent) is also 0,
so we will not hit that if branch.

So, I think Lukas' patch is correct.

Thanks.