linux-kernel - Re: [PATCH v4 1/2] mm: add kstrimdup function

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Date:	Wed, 29 Jan 2014 17:24:28 -0800
From:	Joe Perches <joe@...ches.com>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	Sebastian Capella <sebastian.capella@...aro.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-pm@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, Andrew Morton <akpm@...ux-foundation.org>,
	Michel Lespinasse <walken@...gle.com>,
	Shaohua Li <shli@...nel.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v4 1/2] mm: add kstrimdup function

On Wed, 2014-01-29 at 19:58 -0500, Mikulas Patocka wrote:
> On Wed, 29 Jan 2014, Sebastian Capella wrote:
> > kstrimdup will duplicate and trim spaces from the passed in
> > null terminated string.  This is useful for strings coming from
> > sysfs that often include trailing whitespace due to user input. 
[]
> > diff --git a/mm/util.c b/mm/util.c
[]
> >  /**
> > + * kstrimdup - Trim and copy a %NUL terminated string.
> > + * @s: the string to trim and duplicate
> > + * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> > + *
> > + * Returns an address, which the caller must kfree, containing
> > + * a duplicate of the passed string with leading and/or trailing
> > + * whitespace (as defined by isspace) removed.
> 
> It doesn't remove leading whitespace. To remove them, you need to do
> 
> char *p = strim(ret);
> memmove(ret, p, strlen(p) + 1);
[]
> > + */
> > +char *kstrimdup(const char *s, gfp_t gfp)
> > +{
> > +	char *ret = kstrdup(skip_spaces(s), gfp);
> > +
> > +	if (ret)
> > +		strim(ret);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(kstrimdup);

Why not minimize the malloc length too?

maybe something like:

char *kstrimdup(const char *s, gfp_t gfp)
{
	char *buf;
	const char *begin = skip_spaces(s);
	size_t len = strlen(begin);

	while (len && isspace(begin[len - 1]))
		len--;

	buf = kmalloc_track_caller(len + 1, gfp);
	if (!buf)
		return NULL;

	memcpy(buf, begin, len);
	buf[len] = 0;

	return buf;
}


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