linux-kernel - Re: [PATCH v2 2/2] mm: Covert sysfs input to bool using kstrtobool()

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Message-ID: <Yn6jSElbVPrTJAg9@localhost.localdomain>
Date:   Fri, 13 May 2022 21:28:24 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jagdish Gediya <jvgediya@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Jonathan.Cameron@...wei.com, rf@...nsource.cirrus.com,
        pmladek@...e.com, ying.huang@...el.com, dave.hansen@...el.com
Subject: Re: [PATCH v2 2/2] mm: Covert sysfs input to bool using kstrtobool()

On Thu, May 12, 2022 at 06:05:37PM -0700, Andrew Morton wrote:
> On Wed, 27 Apr 2022 18:17:29 +0300 Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> 
> > On Tue, Apr 26, 2022 at 10:30:40PM +0530, Jagdish Gediya wrote:
> > > Sysfs input conversion to corrosponding bool value e.g. "false" or "0"
> > > to false, "true" or "1" to true are currently handled through strncmp
> > > at multiple places. Use kstrtobool() to convert sysfs input to bool
> > > value.
> > 
> > ...
> > 
> > > +	if (kstrtobool(buf, &numa_demotion_enabled))
> > >  		return -EINVAL;
> > 
> > Hmm... The commit message doesn't explain what's wrong with the error codes
> > returned by kstrtobool(). Can't it be
> > 
> > 	ret = kstrtobool();
> > 	if (ret)
> > 		return ret;
> > 
> > ?
> 
> Jagdish fell asleep.
> 
> Yes, I agree.  It has no practical difference at present because
> kstrtobool() can only return 0 or -EINVAL.  I did this:

	ret = f();
	if (ret)
		return ret;

is slightly better because it doesn't require to load EINVAL into
register:

	call f
	test	eax, eax
	js	1f
	...
1:
	ret