csum_page(struct page *page, int offset, int copy)
{
	char *kaddr;
	unsigned int csum;
	kaddr = kmap(page);
	csum = csum_partial(kaddr + offset, copy, 0);
	kunmap(page);
	return csum;
}
csum_page(struct page *page, int offset, int copy)
{
	char *kaddr;
	unsigned int csum;
	kaddr = kmap(page);
	csum = csum_partial(kaddr + offset, copy, 0);
	kunmap(page);
	return csum;
}