linux-kernel - Re: [PATCH v3 2/5] lib/test_bitmap: add tests for bitmap_{set,get}

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Date:   Mon, 17 Jul 2023 09:11:50 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     catalin.marinas@....com, will@...nel.org, pcc@...gle.com,
        andreyknvl@...il.com, andriy.shevchenko@...ux.intel.com,
        linux@...musvillemoes.dk, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, eugenis@...gle.com,
        syednwaris@...il.com, william.gray@...aro.org
Subject: Re: [PATCH v3 2/5] lib/test_bitmap: add tests for
 bitmap_{set,get}_value()

On Mon, Jul 17, 2023 at 01:37:05PM +0200, Alexander Potapenko wrote:
> Add basic tests ensuring that values can be added at arbitrary positions
> of the bitmap, including those spanning into the adjacent unsigned
> longs.
> 
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
 
Thanks for the test!

> ---
> This patch was previously called
> "lib/test_bitmap: add tests for bitmap_{set,get}_value_unaligned"
> 
> v3:
>  - switch to using bitmap_{set,get}_value()
>  - change the expected bit pattern in test_set_get_value(),
>    as the test was incorrectly assuming 0 is the LSB.
> ---
>  lib/test_bitmap.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> index 187f5b2db4cf1..c2ab54040c249 100644
> --- a/lib/test_bitmap.c
> +++ b/lib/test_bitmap.c
> @@ -71,6 +71,17 @@ __check_eq_uint(const char *srcfile, unsigned int line,
>  	return true;
>  }
>  
> +static bool __init
> +__check_eq_ulong(const char *srcfile, unsigned int line,
> +		 const unsigned long exp_ulong, unsigned long x)
> +{
> +	if (exp_ulong != x) {
> +		pr_err("[%s:%u] expected %lu, got %lu\n",
> +			srcfile, line, exp_ulong, x);
> +		return false;
> +	}
> +	return true;
> +}
>  
>  static bool __init
>  __check_eq_bitmap(const char *srcfile, unsigned int line,
> @@ -186,6 +197,7 @@ __check_eq_str(const char *srcfile, unsigned int line,
>  	})
>  
>  #define expect_eq_uint(...)		__expect_eq(uint, ##__VA_ARGS__)
> +#define expect_eq_ulong(...)		__expect_eq(ulong, ##__VA_ARGS__)
>  #define expect_eq_bitmap(...)		__expect_eq(bitmap, ##__VA_ARGS__)
>  #define expect_eq_pbl(...)		__expect_eq(pbl, ##__VA_ARGS__)
>  #define expect_eq_u32_array(...)	__expect_eq(u32_array, ##__VA_ARGS__)
> @@ -1222,6 +1234,25 @@ static void __init test_bitmap_const_eval(void)
>  	BUILD_BUG_ON(~var != ~BIT(25));
>  }
>  
> +static void __init test_set_get_value(void)
> +{
> +	DECLARE_BITMAP(bitmap, BITS_PER_LONG * 2);

It's too short. Can you make it long enough to ensure it works as
expected when start is not in the 1st word, and start+nbits is in
the following word.

> +	unsigned long val;
> +	int i;
> +
> +	for (i = 0; i < BITS_PER_LONG * 2 - 7; i++) {
> +		bitmap_zero(bitmap, BITS_PER_LONG * 2);
> +		bitmap_set_value(bitmap, 0b10101UL, i, 5);
> +		val = bitmap_get_value(bitmap, i, 5);
> +		expect_eq_ulong(0b10101UL, val);

Can you also check that the rest of bitmap is untouched?
Something like:

	DECLARE_BITMAP(bitmap, ...);
	DECLARE_BITMAP(orig, ...);

        memset(orig, 0x5a, ...);
        memset(bitmap, 0x5a, ...);

        for (j = start; j < start + nbits; j++)
                if (val & BIT(j - start))
                        __set_bit(j, orig);
                else
                        __clear_bit(j, orig);

        bitmap_set_value(bitmap, val, start, nbits);
        expect_eq_bitmap(orig, bitmap, ...);

I like this kind of testing because it gives people a better
understanding of what happens behind all that optimization tricks.

Thanks,
Yury