On Mon, Dec 26 2016, Jaewon Kim wrote:
> There was no bitmap API which returns both next zero index and size of zeros
> from that index.
Is it really needed? Does it noticeably simplifies callers? Why can’t
caller get the size by themselves if they need it?
>
> This is helpful to look fragmentation. This is an test code to look size of zeros.
> Test result is '10+9+994=>1013 found of total: 1024'
>
> unsigned long search_idx, found_idx, nr_found_tot;
> unsigned long bitmap_max;
> unsigned int nr_found;
> unsigned long *bitmap;
>
> search_idx = nr_found_tot = 0;
> bitmap_max = 1024;
> bitmap = kzalloc(BITS_TO_LONGS(bitmap_max) * sizeof(long),
> GFP_KERNEL);
>
> /* test bitmap_set offset, count */
> bitmap_set(bitmap, 10, 1);
> bitmap_set(bitmap, 20, 10);
>
> for (;;) {
> found_idx = bitmap_find_next_zero_area_and_size(bitmap,
> bitmap_max, search_idx, &nr_found);
> if (found_idx >= bitmap_max)
> break;
> if (nr_found_tot == 0)
> printk("%u", nr_found);
> else
> printk("+%u", nr_found);
> nr_found_tot += nr_found;
> search_idx = found_idx + nr_found;
> }
> printk("=>%lu found of total: %lu\n", nr_found_tot, bitmap_max);
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> ---
> include/linux/bitmap.h | 6 ++++++
> lib/bitmap.c | 25 +++++++++++++++++++++++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 3b77588..b724a6c 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -46,6 +46,7 @@
> * bitmap_clear(dst, pos, nbits) Clear specified bit area
> * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
> * bitmap_find_next_zero_area_off(buf, len, pos, n, mask) as above
> + * bitmap_find_next_zero_area_and_size(buf, len, pos, n, mask) Find bit free area and its size
> * bitmap_shift_right(dst, src, n, nbits) *dst = *src >> n
> * bitmap_shift_left(dst, src, n, nbits) *dst = *src << n
> * bitmap_remap(dst, src, old, new, nbits) *dst = map(old, new)(src)
> @@ -123,6 +124,11 @@ extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
> unsigned long align_mask,
> unsigned long align_offset);
>
> +extern unsigned long bitmap_find_next_zero_area_and_size(unsigned long *map,
> + unsigned long size,
> + unsigned long start,
> + unsigned int *nr);
> +
> /**
> * bitmap_find_next_zero_area - find a contiguous aligned zero area
> * @map: The address to base the search on
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 0b66f0e..d02817c 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -332,6 +332,31 @@ unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
> }
> EXPORT_SYMBOL(bitmap_find_next_zero_area_off);
>
> +/**
> + * bitmap_find_next_zero_area_and_size - find a contiguous aligned zero area
> + * @map: The address to base the search on
> + * @size: The bitmap size in bits
> + * @start: The bitnumber to start searching at
> + * @nr: The number of zeroed bits we've found
> + */
> +unsigned long bitmap_find_next_zero_area_and_size(unsigned long *map,
> + unsigned long size,
> + unsigned long start,
> + unsigned int *nr)
> +{
> + unsigned long index, i;
> +
> + *nr = 0;
> + index = find_next_zero_bit(map, size, start);
> +
> + if (index >= size)
> + return index;
> + i = find_next_bit(map, size, index);
> + *nr = i - index;
> + return index;
> +}
> +EXPORT_SYMBOL(bitmap_find_next_zero_area_and_size);
> +
> /*
> * Bitmap printing & parsing functions: first version by Nadia Yvette Chambers,
> * second version by Paul Jackson, third by Joe Korty.
> --
> 1.9.1
>
--
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»
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