linux-kernel - Re: [PATCH 1/6] bitmap_parselist: don't calculate length of the input string

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Message-ID: <20190326100956.GS9224@smile.fi.intel.com>
Date:   Tue, 26 Mar 2019 12:09:56 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Yury Norov <ynorov@...vell.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] bitmap_parselist: don't calculate length of the
 input string

On Tue, Mar 26, 2019 at 12:07:43AM +0300, Yury Norov wrote:
> bitmap_parselist() calculates length of the input string before passing
> it to the __bitmap_parselist(). But the end-of-line condition is checked
> for every character in __bitmap_parselist() anyway. So doing it in wrapper
> is a simple waste of time.

This is not best change, I think. See my further comments.

> 
> Signed-off-by: Yury Norov <ynorov@...vell.com>
> ---
>  lib/bitmap.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 98872e9025da..ad1fb7e6ad0e 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -614,10 +614,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>  
>  int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
>  {
> -	char *nl  = strchrnul(bp, '\n');
> -	int len = nl - bp;
> -
> -	return __bitmap_parselist(bp, len, 0, maskp, nmaskbits);
> +	return __bitmap_parselist(bp, UINT_MAX, 0, maskp, nmaskbits);
>  }
>  EXPORT_SYMBOL(bitmap_parselist);
>  
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko