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

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Date:   Tue, 26 Jan 2021 19:12:58 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        lizefan@...wei.com, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, josh@...htriplett.org,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, fweisbec@...il.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH 4/8] lib: bitmap: move ERANGE check from set_region to check_region

On Tue, Jan 26, 2021 at 9:12 AM Paul Gortmaker
<paul.gortmaker@...driver.com> 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...
>
> Cc: Yury Norov <yury.norov@...il.com>
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> ---
>  lib/bitmap.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 162e2850c622..833f152a2c43 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -500,17 +500,12 @@ struct region {
>         unsigned int nbits;
>  };
>
> -static int bitmap_set_region(const struct region *r, unsigned long *bitmap)
> +static void bitmap_set_region(const struct region *r, unsigned long *bitmap)
>  {
>         unsigned int start;
>
> -       if (r->end >= r->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)
> @@ -518,6 +513,9 @@ static int bitmap_check_region(const struct region *r)
>         if (r->start > r->end || r->group_len == 0 || r->off > r->group_len)
>                 return -EINVAL;
>
> +       if (r->end >= r->nbits)
> +               return -ERANGE;
> +
>         return 0;
>  }
>
> @@ -656,9 +654,7 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
>                 if (ret)
>                         return ret;
>
> -               ret = bitmap_set_region(&r, maskp);
> -               if (ret)
> -                       return ret;
> +               bitmap_set_region(&r, maskp);
>         }
>
>         return 0;
> --
> 2.17.1

Acked-by: Yury Norov <yury.norov@...il.com>