netdev - Re: [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings

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Message-ID: <CAK8P3a3nUCGwPpE+E820DniY8Haz1Xx72pA38P6s5MWsbi0iAQ@mail.gmail.com>
Date:   Tue, 30 Mar 2021 11:00:36 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Martin Sebor <msebor@....gnu.org>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Ning Sun <ning.sun@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Simon Kelley <simon@...kelleys.org.uk>,
        James Smart <james.smart@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Anders Larsen <al@...rsen.net>,
        Serge Hallyn <serge@...lyn.com>,
        Imre Deak <imre.deak@...el.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        tboot-devel@...ts.sourceforge.net,
        Intel Graphics <intel-gfx@...ts.freedesktop.org>,
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        Roman Gushchin <guro@...com>,
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        Andrii Nakryiko <andriin@...com>, Odin Ugedal <odin@...d.al>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Bhaskar Chowdhury <unixbhaskar@...il.com>
Subject: Re: [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings

On Tue, Mar 30, 2021 at 10:41 AM Michal Koutný <mkoutny@...e.com> wrote:
>
> On Mon, Mar 22, 2021 at 05:02:44PM +0100, Arnd Bergmann <arnd@...nel.org> wrote:
> > I'm not sure what is expected to happen for such a configuration,
> > presumably these functions are never calls in that case.
> Yes, the functions you patched would only be called from subsystems or
> there should be no way to obtain a struct cgroup_subsys reference
> anyway (hence it's ok to always branch as if ss==NULL).
>
> I'd prefer a variant that wouldn't compile the affected codepaths when
> there are no subsystems registered, however, I couldn't come up with a
> way how to do it without some preprocessor ugliness.

Would it be possible to enclose most or all of kernel/cgroup/cgroup.c
in an #ifdef CGROUP_SUBSYS_COUNT block? I didn't try that
myself, but this might be a way to guarantee that there cannot
be any callers (it would cause a link error).

> Reviewed-by: Michal Koutný <mkoutny@...e.com>

Thanks

        Arnd