리눅스 디바이스 드라이버에서 할당받은 메모리 페이지를 해제하려면 어떻게 해야하나요?

int simple_fault_handler(struct vm_area_struct *vma, struct vm_fault *vmf){
	printk(KERN_INFO " page fault occurred\n");	
	if(flag_ops==1){
		__free_pages(page_ops, 0);
		//put_page(page_ops);
		printk(KERN_INFO "unmap pages\n");
	}
	if(flag_ops==0)
	{
		kaddr_ops=kmalloc(4096, GFP_KERNEL);
		//page_ops = virt_to_page(((unsigned long)kaddr_ops + (unsigned long)(vmf->virtual_address - vma->vm_start)) & PAGE_MASK);
		flag_ops=1;
	}
	page_ops = virt_to_page(((unsigned long)kaddr_ops + (unsigned long)(vmf->virtual_address - vma->vm_start)) & PAGE_MASK);
	vmf->page=page_ops;
  	get_page(vmf->page);
 
	return 0;
}
static struct vm_operations_struct simple_remap_vm_ops = {
	.open =  simple_vma_open,
	.close = simple_vma_close,
	.fault = simple_fault_handler,
};
 
static int simple_remap_mmap(struct file *filp, struct vm_area_struct *vma)
{
	vma->vm_ops = &simple_remap_vm_ops;
	return 0;
}
static struct file_operations simple_remap_ops = {
	.owner   = THIS_MODULE,
	.open    = simple_opens,
	.release = simple_release,
	.mmap    = simple_remap_mmap,
};