static int ion_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct ion_buffer *buffer = vma->vm_private_data;
	unsigned long pfn;
	int ret;

	mutex_lock(&buffer->lock);
	ion_buffer_page_dirty(buffer->pages + vmf->pgoff);
	BUG_ON(!buffer->pages || !buffer->pages[vmf->pgoff]);

	pfn = page_to_pfn(ion_buffer_page(buffer->pages[vmf->pgoff]));
	ret = vm_insert_pfn(vma, (unsigned long)vmf->virtual_address, pfn);
	mutex_unlock(&buffer->lock);
	if (ret)
		return VM_FAULT_ERROR;

	return VM_FAULT_NOPAGE;
}
static int ion_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct ion_buffer *buffer = vma->vm_private_data;
	unsigned long pfn;
	int ret;

	mutex_lock(&buffer->lock);
	ion_buffer_page_dirty(buffer->pages + vmf->pgoff);
	BUG_ON(!buffer->pages || !buffer->pages[vmf->pgoff]);

	pfn = page_to_pfn(ion_buffer_page(buffer->pages[vmf->pgoff]));
	ret = vm_insert_pfn(vma, (unsigned long)vmf->virtual_address, pfn);
	mutex_unlock(&buffer->lock);
	if (ret)
		return VM_FAULT_ERROR;

	return VM_FAULT_NOPAGE;
}