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

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Message-ID: <CAG_fn=XnyrYwMdM5i-KqpaxW0xG+vFs3h3nipKePe8yTo23Eug@mail.gmail.com>
Date:   Mon, 17 Jul 2023 18:42:47 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Yury Norov <yury.norov@...il.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 6:11 PM Yury Norov <yury.norov@...il.com> wrote:
>
> 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.

Will do. In fact the difference between GENMASK(n, 0) and GENMASK(n-1,
0) discussed in the other patch requires exactly this kind of testing.