Kamezawa Hiroyuki [off-list ref] writes:

You can use other pages than head/tails.
For example,I think you have 512 pages per 2M pages.

How about the below. This limit the usage to hugetlb cgroup to only
hugepages with more than 3 normal pages. I guess that is an acceptable limitation.

static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
{
	if (!PageHuge(page))
		return NULL;
	if (compound_order(page) < 3)
		return NULL;
	return (struct hugetlb_cgroup *)page[2].lru.next;
}

static inline
int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
{
	if (!PageHuge(page))
		return -1;
	if (compound_order(page) < 3)
		return -1;
	page[2].lru.next = (void *)h_cg;
	return 0;
}


-aneesh