Re: [PATCH v4 2/2] lib/bitmap: add tests for bitmap_find_next_zero_area_off()

[Yury Norov]

(Sorry, hit 'send' prematurely with a fat finger)

On Mon, Jun 08, 2026 at 03:14:22PM -0400, Yury Norov wrote:
> On Mon, Jun 01, 2026 at 05:42:34PM +0800, Yi Sun wrote:
> > Add functional and performance tests
> > for bitmap_find_next_zero_area_off().
> > 
> > Signed-off-by: Yi Sun <yi.sun@xxxxxxxxxx>
> > ---
> >  lib/find_bit_benchmark.c | 17 +++++++++++++++++
> >  lib/test_bitmap.c        | 28 ++++++++++++++++++++++++++++
> >  2 files changed, 45 insertions(+)
> > 
> > diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c
> > index 00d9dc61cd46..37fe76ad322e 100644
> > --- a/lib/find_bit_benchmark.c
> > +++ b/lib/find_bit_benchmark.c
> > @@ -149,6 +149,21 @@ static int __init test_find_next_and_bit(const void *bitmap,
> >  	return 0;
> >  }
> >  
> > +static int __init
> > +test_bitmap_find_next_zero_area_off(unsigned long *bitmap, unsigned long len)
> > +{
> > +	unsigned long i, cnt;
> > +	ktime_t time;
> > +
> > +	time = ktime_get();
> > +	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
> > +		i = bitmap_find_next_zero_area_off(bitmap, BITMAP_LEN, i, 8, 0, 0) + 1;
> > +	time = ktime_get() - time;
> > +	pr_err("bitmap_find_next_zero_area_off:  %18llu ns, %6ld iterations\n", time, cnt);
> > +
> > +	return 0;
> > +}

I asked you at least 3 times to print the exact test output in the
commit message. If you didn't ignore it, you'd see something like:

[    0.230280] Start testing find_bit() with random-filled bitmap
[    0.231438] bitmap_find_next_zero_area_off:              352393 ns,   1235 iterations
[    0.232771] find_next_bit:                  586225 ns, 163838 iterations
[    0.234022] find_next_zero_bit:             631854 ns, 163843 iterations
[    0.235154] find_last_bit:                  489426 ns, 163839 iterations
[    0.238080] find_nth_bit:                  2283610 ns,  16471 iterations
[    0.239545] find_first_bit:                 844551 ns,  16472 iterations
[    0.248981] find_first_and_bit:            8840955 ns,  41232 iterations
[    0.250030] find_next_and_bit:              334729 ns,  81913 iterations
[    0.250728]
[    0.250728] Start testing find_bit() with sparse bitmap
[    0.253094] bitmap_find_next_zero_area_off:             1658964 ns, 322485 iterations
[    0.253851] find_next_bit:                    8053 ns,    655 iterations
[    0.255664] find_next_zero_bit:            1247380 ns, 327026 iterations
[    0.256292] find_last_bit:                    7444 ns,    655 iterations
[    0.257756] find_nth_bit:                   865494 ns,    654 iterations
[    0.258720] find_first_bit:                 284844 ns,    655 iterations
[    0.259347] find_first_and_bit:               1824 ns,      1 iterations
[    0.259992] find_next_and_bit:                1763 ns,      1 iterations

And it clearly breaks the test format. Please, when it comes to v5,
double check that you have all reviewers requests addressed.

> > +
> >  static int __init find_bit_test(void)
> >  {
> >  	unsigned long nbits = BITMAP_LEN / SPARSE;
> > @@ -158,6 +173,7 @@ static int __init find_bit_test(void)
> >  	get_random_bytes(bitmap, sizeof(bitmap));
> >  	get_random_bytes(bitmap2, sizeof(bitmap2));
> >  
> > +	test_bitmap_find_next_zero_area_off(bitmap, BITMAP_LEN);
> >  	test_find_next_bit(bitmap, BITMAP_LEN);
> >  	test_find_next_zero_bit(bitmap, BITMAP_LEN);
> >  	test_find_last_bit(bitmap, BITMAP_LEN);
> > @@ -181,6 +197,7 @@ static int __init find_bit_test(void)
> >  		__set_bit(get_random_u32_below(BITMAP_LEN), bitmap2);
> >  	}
> >  
> > +	test_bitmap_find_next_zero_area_off(bitmap, BITMAP_LEN);
> >  	test_find_next_bit(bitmap, BITMAP_LEN);
> >  	test_find_next_zero_bit(bitmap, BITMAP_LEN);
> >  	test_find_last_bit(bitmap, BITMAP_LEN);
> > diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
> > index 69813c10e6c0..fad2b19760c2 100644
> > --- a/lib/test_bitmap.c
> > +++ b/lib/test_bitmap.c
> > @@ -234,6 +234,34 @@ static void __init test_find_nth_bit(void)
> >  	}
> >  }
> >  
> > +static void __init
> > +test_bitmap_find_next_zero_area_off(void)
> 
> warning: ‘test_bitmap_find_next_zero_area_off’ defined but not used [-Wunused-function]
>   238 | test_bitmap_find_next_zero_area_off(void)
> 
> > +{
> > +	int bmap_len = 64 * 3;
> > +	DECLARE_BITMAP(bmap, bmap_len);
> 
> I believe, everyone can realize that 64*3 == 192, and we don't need a
> variable for it.
> 
> > +	bitmap_set(bmap, 0, bmap_len);
> > +
> > +	bitmap_clear(bmap, 0, 8);
> > +	__clear_bit(50, bmap);
> > +	bitmap_clear(bmap, 60, 10);
> > +	__clear_bit(80, bmap);
> > +	bitmap_clear(bmap, 100, 10);
> > +	__clear_bit(120, bmap);
> > +	bitmap_clear(bmap, 160, 32);
> 
> Can you also test a 'dirty' region:
> 
>         bitmap_clear(60, 18);
>         __set_bit(69);
>         // find nothing
>         bitmap_find_next_zero_area_off(bmap, bmap_len, 0, 10, 0, 0));
> 
> > +
> > +	expect_eq_uint(0,
> > +		bitmap_find_next_zero_area_off(bmap, bmap_len, 0, 8, 0, 0));
> > +	expect_eq_uint(60,
> > +		bitmap_find_next_zero_area_off(bmap, bmap_len, 1, 8, 0, 0));
> > +	expect_eq_uint(60,
> > +		bitmap_find_next_zero_area_off(bmap, bmap_len, 0, 10, 0, 0));
> > +	expect_eq_uint(160,
> > +		bitmap_find_next_zero_area_off(bmap, bmap_len, 0, 32, 0, 0));
> > +	expect_eq_uint(1,
> > +		!!(bitmap_find_next_zero_area_off(bmap, bmap_len, 0, 33, 0, 0) > bmap_len));
> 
> Two last parameters are zero in all cases. Doesn't sound like an
> exhaustive testing. Real users provide non-zero alignments, so please
> you do.
> 
> > +}
> > +
> >  static void __init test_fill_set(void)
> >  {
> >  	DECLARE_BITMAP(bmap, 1024);
> > -- 
> > 2.34.1