Re: [Qemu-devel] [PATCH 08/10] qcow2: Allow updating no refcounts

[Christoph Hellwig]

>  #endif
> -    if (length <= 0)
> +    if (length < 0) {
>          return -EINVAL;
> +    }
> +
>      start = offset & ~(s->cluster_size - 1);
>      last = (offset + length - 1) & ~(s->cluster_size - 1);
>      for(cluster_offset = start; cluster_offset <= last;

So for legnth = 0, last will equal start and we'll never go through
the loop.  But should we really bother with all the other work in the
function or just return 0 early on?