Re: [Qemu-devel] [PATCH 1/5] hbitmap: add next_zero function

[Eric Blake]

On 10/02/2017 09:39 AM, Vladimir Sementsov-Ogievskiy wrote:
> The function searches for next zero bit.
> Also add interface for BdrvDirtyBitmap.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  include/block/dirty-bitmap.h |  1 +
>  include/qemu/hbitmap.h       |  8 ++++++++
>  block/dirty-bitmap.c         |  5 +++++
>  util/hbitmap.c               | 29 +++++++++++++++++++++++++++++
>  4 files changed, 43 insertions(+)
> 

> +++ b/block/dirty-bitmap.c
> @@ -715,3 +715,8 @@ char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap 
> *bitmap, Error **errp)
>  {
>      return hbitmap_sha256(bitmap->bitmap, errp);
>  }
> +
> +int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t offset)
> +{
> +    return hbitmap_next_zero(bitmap->bitmap, offset);
> +}

Returns an answer in the same scale as the underlying hbitmap; if this
is applied before my byte-based dirty bitmap series, that means offset
is a sector count and the result is likewise a sector number (awkward);
if this is applied after my series, you pass in a byte offset start and
get a byte result (nice).

I don't see any obvious errors in the implementation, but DO think that
you should include a testsuite enhancement in tests/test-hbitmap.c to
cover the new functionality before we accept this.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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