Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight_eq()

Michał Mirosław
2021-11-28T18:12:30Z

On Sat, Nov 27, 2021 at 07:56:57PM -0800, Yury Norov wrote:
> Now as we have bitmap_weight_eq(), switch bitmap_full() and
> bitmap_empty() to using it.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
> include/linux/bitmap.h | 26 ++++++++++----------------
> 1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 996041f771c8..2d951e4dc814 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -386,22 +386,6 @@ static inline int bitmap_subset(const unsigned long *src1,
> return __bitmap_subset(src1, src2, nbits);
> }
>
> -static inline bool bitmap_empty(const unsigned long *src, unsigned nbits)
> -{
> - if (small_const_nbits(nbits))
> - return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
> -
> - return find_first_bit(src, nbits) == nbits;
> -}

Since this is supposed to be an optimization, I would go all the way and
replace this with the trivial implementation instead:

bool bitmap_empty(long *bits, size_t nbits)
{
for (; nbits >= BITS_PER_LONG; ++bits, nbits -= BITS_PER_LONG)
if (*bits)
return false;

if (nbits && *bits & BITMAP_LAST_WORD_MASK(nbits))
return false;

return true;
}

Best Regards
Michał Mirosław