Re: [Qemu-devel] [PATCH v2 5/9] hbitmap: Add hbitmap_copy

[Benoît Canet]

The Wednesday 12 Mar 2014 à 14:31:00 (+0800), Fam Zheng wrote :
> This makes a deep copy of an HBitmap.
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  include/qemu/hbitmap.h |  8 ++++++++
>  util/hbitmap.c         | 13 +++++++++++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
> index 550d7ce..b645cfc 100644
> --- a/include/qemu/hbitmap.h
> +++ b/include/qemu/hbitmap.h
> @@ -65,6 +65,14 @@ struct HBitmapIter {
>  HBitmap *hbitmap_alloc(uint64_t size, int granularity);
>
>  /**
> + * hbitmap_copy:
> + * @bitmap: The original bitmap to copy.
> + *
> + * Copy a HBitmap.
> + */
> +HBitmap *hbitmap_copy(const HBitmap *bitmap);
> +
> +/**
>   * hbitmap_empty:
>   * @hb: HBitmap to operate on.
>   *
> diff --git a/util/hbitmap.c b/util/hbitmap.c
> index d936831..cf670c7 100644
> --- a/util/hbitmap.c
> +++ b/util/hbitmap.c
> @@ -400,3 +400,16 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity)
>      hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
>      return hb;
>  }
> +
> +HBitmap *hbitmap_copy(const HBitmap *bitmap)
> +{
> +    int i;
> +    HBitmap *hb = g_memdup(bitmap, sizeof(struct HBitmap));
> +
> +    for (i = HBITMAP_LEVELS; i-- > 0; ) {
> +        hb->levels[i] = g_memdup(bitmap->levels[i],
> +                                 bitmap->size * sizeof(unsigned long));

This feel wrong:

struct HBitmap {
    /* Number of total bits in the bottom level.  */
    uint64_t size;

The comment about size imply that size apply only to the bottom level.

Moreover the bitmaps are progressivelly less coarse so I think the size you use
should goes down as you go up to the top.

Best regards

Benoît

> +    }
> +
> +    return hb;
> +}
> --
> 1.9.0
>
>