On Thu 22-12-22 22:33:49, Kemeng Shi wrote:
> We calculate allow_hint in next word as following:
>
> /* low sb->shift bit of alloc_hint will be 0 after this shift */
> alloc_hint = index << sb->shift;
>
> /* get low sb->shift bit of alloc_hit */
> SB_NR_TO_BIT(sb, alloc_hint)
>
> So alloc_hit in next word will always be zero. Simpfy alloc_hit calculation
> in __sbitmap_get_shallow according to the alloc_hit calculation in
> __sbitmap_get.
>
> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Looks good to me, nice cleanup. I'd just somewhat rephrase the changelog
to:
Updates to alloc_hint in the loop in __sbitmap_get_shallow() are mostly
pointless and equivalent to setting alloc_hint to zero (because
SB_NR_TO_BIT() considers only low sb->shift bits from alloc_hint). So
simplify the logic.
Anyway, feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> lib/sbitmap.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c
> index 586deb333237..cb5e03a2d65b 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -243,6 +243,7 @@ static int __sbitmap_get_shallow(struct sbitmap *sb,
> int nr = -1;
>
> index = SB_NR_TO_INDEX(sb, alloc_hint);
> + alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
>
> for (i = 0; i < sb->map_nr; i++) {
> again:
> @@ -250,7 +251,7 @@ static int __sbitmap_get_shallow(struct sbitmap *sb,
> min_t(unsigned int,
> __map_depth(sb, index),
> shallow_depth),
> - SB_NR_TO_BIT(sb, alloc_hint), true);
> + alloc_hint, true);
> if (nr != -1) {
> nr += index << sb->shift;
> break;
> @@ -260,13 +261,9 @@ static int __sbitmap_get_shallow(struct sbitmap *sb,
> goto again;
>
> /* Jump to next index. */
> - index++;
> - alloc_hint = index << sb->shift;
> -
> - if (index >= sb->map_nr) {
> + alloc_hint = 0;
> + if (++index >= sb->map_nr)
> index = 0;
> - alloc_hint = 0;
> - }
> }
>
> return nr;
> --
> 2.30.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
