linux-kernel - Re: [PATCH] lib/string: Introduce sysfs

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Date:   Thu, 8 Apr 2021 09:25:29 +0200
From:   Gioh Kim <gi-oh.kim@...os.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        laniel_francis@...vacyrequired.com,
        Kees Cook <keescook@...omium.org>,
        Daniel Axtens <dja@...ens.net>
Subject: Re: [PATCH] lib/string: Introduce sysfs_streqcase

On Wed, Apr 7, 2021 at 10:07 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Tue, Apr 6, 2021 at 11:15 PM Gioh Kim <gi-oh.kim@...os.com> wrote:
> >
> > As the name shows, it checks if strings are equal in case insensitive
> > manner.
> >
> > For example, drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c uses
> > strncasecmp to check that the input via sysfs is "mi". But it would
> > work even-if the input is "min-wrongcommand".
> >
> > I found some more cases using strncasecmp to check the entire string
> > such as rtrs-clt-sysfs.c does. drivers/pnp/interface.c checks
> > "disable" command with strncasecmp but it would also work if the
> > command is "disable-wrong".
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> I do wonder if these (sysfs_streqcase and sysfs_streq) could or should
> be conditionally available on CONFIG_SYSFS=y; don't pay for what you
> don't use (without needing CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y)?

Good idea.
Thank you.

>
> Also, it might be nice to share the second half of the function with
> sysfs_streq via a new static function.  Though it will just get
> inlined in both for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y, it might
> help the compiler if CONFIG_CC_OPTIMIZE_FOR_SIZE=y was instead chosen
> if the compiler cannot outline/deduplicate the shared code.  At the
> least, there's less duplication between two very similar functions; if
> one changes then authors may need to be careful to update both.

Yes, they are exactly the same.
I will make an inline function for the common code.

>
> Are either of those concerns worth a v3? ¯\_(ツ)_/¯

Sure, I will not forget to add 'V2'.

Thank you for kind review.