linux-kernel - Re: [PATCH 30/54] drivers/memstick: replace bitmap_weight with bitmap_weight

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Message-ID: <CAPDyKFoJ=1nTYh6rNUQV2X68qE+jJX3OEindnTN_2_J54UVqkA@mail.gmail.com>
Date:   Mon, 31 Jan 2022 17:07:10 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <david.laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org,
        Maxim Levitsky <maximlevitsky@...il.com>,
        Alex Dubov <oakad@...oo.com>, Jens Axboe <axboe@...nel.dk>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Colin Ian King <colin.king@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        Shubhankar Kuranagatti <shubhankarvk@...il.com>,
        linux-mmc@...r.kernel.org
Subject: Re: [PATCH 30/54] drivers/memstick: replace bitmap_weight with
 bitmap_weight_eq where appropriate

On Sun, 23 Jan 2022 at 19:41, Yury Norov <yury.norov@...il.com> wrote:
>
> msb_validate_used_block_bitmap() calls bitmap_weight() to compare the
> weight of bitmap with a given number. We can do it more efficiently with
> bitmap_weight_eq because conditional bitmap_weight may stop traversing the
> bitmap earlier, as soon as condition is met.
>
> Signed-off-by: Yury Norov <yury.norov@...il.com>

Acked-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  drivers/memstick/core/ms_block.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/memstick/core/ms_block.c b/drivers/memstick/core/ms_block.c
> index 0cda6c6baefc..5cdd987e78f7 100644
> --- a/drivers/memstick/core/ms_block.c
> +++ b/drivers/memstick/core/ms_block.c
> @@ -155,8 +155,8 @@ static int msb_validate_used_block_bitmap(struct msb_data *msb)
>         for (i = 0; i < msb->zone_count; i++)
>                 total_free_blocks += msb->free_block_count[i];
>
> -       if (msb->block_count - bitmap_weight(msb->used_blocks_bitmap,
> -                                       msb->block_count) == total_free_blocks)
> +       if (bitmap_weight_eq(msb->used_blocks_bitmap, msb->block_count,
> +                               msb->block_count - total_free_blocks))
>                 return 0;
>
>         pr_err("BUG: free block counts don't match the bitmap");
> --
> 2.30.2
>