Re: [PATCH v2 03/35] lib/sbitmap; make __sbitmap_get_word() using find_and_set_bit()

Jan Kara
2023-12-04T18:22:34Z

On Sun 03-12-23 11:32:35, Yury Norov wrote:
> __sbitmap_get_word() opencodes either find_and_set_bit_wrap(), or
> find_and_set_next_bit() depending on hint and wrap parameters.
>
> Switch it to use the atomic find_bit() API. While here, simplify
> sbitmap_find_bit_in_word(), which calls it.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> lib/sbitmap.c | 46 ++++++++--------------------------------------
> 1 file changed, 8 insertions(+), 38 deletions(-)
>
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c
> index d0a5081dfd12..b21aebd07fd6 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -133,38 +133,11 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
> }
> EXPORT_SYMBOL_GPL(sbitmap_resize);
>
> -static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
> +static inline int __sbitmap_get_word(unsigned long *word, unsigned long depth,
> unsigned int hint, bool wrap)
> {
> - int nr;
> -
> - /* don't wrap if starting from 0 */
> - wrap = wrap && hint;
> -
> - while (1) {
> - nr = find_next_zero_bit(word, depth, hint);
> - if (unlikely(nr >= depth)) {
> - /*
> - * We started with an offset, and we didn't reset the
> - * offset to 0 in a failure case, so start from 0 to
> - * exhaust the map.
> - */
> - if (hint && wrap) {
> - hint = 0;
> - continue;
> - }
> - return -1;
> - }
> -
> - if (!test_and_set_bit_lock(nr, word))
> - break;
> -
> - hint = nr + 1;
> - if (hint >= depth - 1)
> - hint = 0;
> - }
> -
> - return nr;
> + return wrap ? find_and_set_bit_wrap_lock(word, depth, hint) :
> + find_and_set_next_bit_lock(word, depth, hint);
> }
>
> static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
> @@ -175,15 +148,12 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
> int nr;
>
> do {
> - nr = __sbitmap_get_word(&map->word, depth,
> - alloc_hint, wrap);
> - if (nr != -1)
> - break;
> - if (!sbitmap_deferred_clear(map))
> - break;
> - } while (1);
> + nr = __sbitmap_get_word(&map->word, depth, alloc_hint, wrap);
> + if (nr < depth)
> + return nr;
> + } while (sbitmap_deferred_clear(map));
>
> - return nr;
> + return -1;
> }
>
> static int sbitmap_find_bit(struct sbitmap *sb,
> --
> 2.40.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR