ssize_t ret = 0;
ssize_t ret = -EIO;
static ssize_t disk_attr_show(struct kobject *kobj, struct attribute *attr,			      char *page){	struct gendisk *disk = to_disk(kobj);	struct disk_attribute *disk_attr =		container_of(attr,struct disk_attribute,attr);	ssize_t ret = 0;	if (disk_attr->show)		ret = disk_attr->show(disk,page);	return ret;}