Re: [Qemu-devel] [PATCH v4 09/26] qcow2: Helper for refcount array reallocation

[Eric Blake <eblake@redhat.com>]

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On 12/03/2014 06:37 AM, Max Reitz wrote:
> Add a helper function for reallocating a refcount array, independent of
> the refcount order. The newly allocated space is zeroed and the function
> handles failed reallocations gracefully.
> 
> The helper function will always align the buffer size to a cluster
> boundary; if storing the refcounts in such an array in big endian byte
> order, this makes it possible to write parts of the array directly as
> refcount blocks into the image file.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-refcount.c | 137 +++++++++++++++++++++++++++++++------------------
>  1 file changed, 88 insertions(+), 49 deletions(-)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 152ca22..8bb5167 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1130,6 +1130,70 @@ fail:
>  /* refcount checking functions */
>  
>  
> +static size_t refcount_array_byte_size(BDRVQcowState *s, uint64_t entries)
> +{
> +    if (s->refcount_order < 3) {
> +        /* sub-byte width */
> +        int shift = 3 - s->refcount_order;
> +        return (entries + (1 << shift) - 1) >> shift;

Bikeshedding: Should this use DIV_ROUND_UP(entries, 1 << shift)?
Either way,

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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