vdisk_info
STAILQ_REMOVE(&vdisk_list, vd, vdisk_info, vdisk_link);
typedef STAILQ_HEAD(vdisk_info_list, vdisk_info) vdisk_info_list_t;
STAILQ_ENTRY(vdisk_info) vdisk_link; /* link in device list */
int vdevice, uint16_t vdisk_info, unsigned long sector_size,
uint16_t vdisk_info, unsigned long sector_size,