Re: [PATCH v3] mm/hugetlb: fix memory offline with hugepage size > memory block size

Dave Hansen
2016-09-22T18:12:26Z

On 09/22/2016 09:29 AM, Gerald Schaefer wrote:
> static void dissolve_free_huge_page(struct page *page)
> {
> + struct page *head = compound_head(page);
> + struct hstate *h = page_hstate(head);
> + int nid = page_to_nid(head);
> +
> spin_lock(&hugetlb_lock);
> - if (PageHuge(page) && !page_count(page)) {
> - struct hstate *h = page_hstate(page);
> - int nid = page_to_nid(page);
> - list_del(&page->lru);
> - h->free_huge_pages--;
> - h->free_huge_pages_node[nid]--;
> - h->max_huge_pages--;
> - update_and_free_page(h, page);
> - }
> + list_del(&head->lru);
> + h->free_huge_pages--;
> + h->free_huge_pages_node[nid]--;
> + h->max_huge_pages--;
> + update_and_free_page(h, head);
> spin_unlock(&hugetlb_lock);
> }

Do you need to revalidate anything once you acquire the lock? Can this,
for instance, race with another thread doing vm.nr_hugepages=0? Or a
thread faulting in and allocating the large page that's being dissolved?