mm/dynamic_hugetlb: fix compound_nr incorrect

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I641XX
CVE: NA

--------------------------------

Patch 1378a5ee ("mm: store compound_nr as well as compound_order") add
a new member compound_nr in struct page, and use this new member insteal
of compound_order in hugetlb_cgroup_move_parent() to compute the nr_pages.

In free_hugepage_to_hugetlb(), we reset page->mapping to NULL for each
subpage. Since page->mapping and page->compound_nr is union, we reset
page->compound_nr too unexpectly. This will finally result the nr_pages
incorrect in hugetlb_cgroup_move_parent() and can't release hugetlb_cgroup.

Fix this problem by reset page->compound_nr using set_compound_order().
Signed-off-by: NLiu Shixin <liushixin2@huawei.com>
Reviewed-by: NNanyong Sun <sunnanyong@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/dynamic_hugetlb.c

@@ -799,7 +799,8 @@ static int free_hugepage_to_hugetlb(struct dhugetlb_pool *hpool)
 			p->mapping = NULL;
 		}
 		set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
-
+		/* compound_nr and mapping are union in page, reset it. */
+		set_compound_order(page, PUD_SHIFT - PAGE_SHIFT);
 		nid = page_to_nid(page);
 		SetHPageFreed(page);
 		list_move(&page->lru, &h->hugepage_freelists[nid]);