Re: [Qemu-devel] [PATCH v3 06/22] qcow2: Helper for refcount array reallocation

[Eric Blake <eblake@redhat.com>]

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On 11/20/2014 10:06 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>
> Reviewed-by: Eric Blake <eblake@redhat.com>

Perhaps the changes since v2 warranted removing my earlier R-b to make
sure I review closely?

> ---
>  block/qcow2-refcount.c | 135 +++++++++++++++++++++++++++++++------------------
>  1 file changed, 86 insertions(+), 49 deletions(-)
> 

> +static int realloc_refcount_array(BDRVQcowState *s, uint16_t **array,
> +                                  int64_t *size, int64_t new_size)
> +{
> +    /* Round to clusters so the array can be directly written to disk */
> +    size_t old_byte_size = ROUND_UP(refcount_array_byte_size(s, *size),
> +                                    s->cluster_size);
> +    size_t new_byte_size = ROUND_UP(refcount_array_byte_size(s, new_size),
> +                                    s->cluster_size);
> +    uint16_t *new_ptr;
> +
> +    if (new_byte_size <= old_byte_size) {
> +        *size = new_size;
> +        return 0;
> +    }
> +
> +    assert(new_byte_size > 0);

Should this assert be moved before the early exit?

Hmm, that's my only finding, and you did incorporate improvements mostly
to comments or asserts as compared to v2.  Moving the assert is small
enough, and not a show-stopper if you leave it in place, so:

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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