linux-kernel - Re: [PATCH 4/8] lib: bitmap: move ERANGE check from set_region to check

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Message-ID: <YCQJr8iRDiiZJQpF@smile.fi.intel.com>
Date:   Wed, 10 Feb 2021 18:28:31 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:     linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
        Ingo Molnar <mingo@...nel.org>,
        Yury Norov <yury.norov@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Triplett <josh@...htriplett.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH 4/8] lib: bitmap: move ERANGE check from set_region to
 check_region

On Tue, Feb 09, 2021 at 05:59:03PM -0500, Paul Gortmaker wrote:
> It makes sense to do all the checks in check_region() and not 1/2
> in check_region and 1/2 in set_region.
> 
> Since set_region is called immediately after check_region, the net
> effect on runtime is zero, but it gets rid of an if (...) return...

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Cc: Yury Norov <yury.norov@...il.com>
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Acked-by: Yury Norov <yury.norov@...il.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> ---
>  lib/bitmap.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 75006c4036e9..9596ba53c36b 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -499,25 +499,22 @@ struct region {
>  	unsigned int end;
>  };
>  
> -static int bitmap_set_region(const struct region *r,
> -				unsigned long *bitmap, int nbits)
> +static void bitmap_set_region(const struct region *r, unsigned long *bitmap)
>  {
>  	unsigned int start;
>  
> -	if (r->end >= nbits)
> -		return -ERANGE;
> -
>  	for (start = r->start; start <= r->end; start += r->group_len)
>  		bitmap_set(bitmap, start, min(r->end - start + 1, r->off));
> -
> -	return 0;
>  }
>  
> -static int bitmap_check_region(const struct region *r)
> +static int bitmap_check_region(const struct region *r, int nbits)
>  {
>  	if (r->start > r->end || r->group_len == 0 || r->off > r->group_len)
>  		return -EINVAL;
>  
> +	if (r->end >= nbits)
> +		return -ERANGE;
> +
>  	return 0;
>  }
>  
> @@ -651,13 +648,11 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
>  		if (IS_ERR(buf))
>  			return PTR_ERR(buf);
>  
> -		ret = bitmap_check_region(&r);
> +		ret = bitmap_check_region(&r, nmaskbits);
>  		if (ret)
>  			return ret;
>  
> -		ret = bitmap_set_region(&r, maskp, nmaskbits);
> -		if (ret)
> -			return ret;
> +		bitmap_set_region(&r, maskp);
>  	}
>  
>  	return 0;
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko