* @zone_size_log2: log2 of the zone size in bytes if it is a power of 2 or 0
* if the zone size is not a power of 2.
* @nr_zones: number of zones
* @refcount: number of fio files that share this structure
* @num_open_zones: number of open zones
* @zone_size_log2: log2 of the zone size in bytes if it is a power of 2 or 0
* if the zone size is not a power of 2.
* @nr_zones: number of zones
* @refcount: number of fio files that share this structure
* @num_open_zones: number of open zones