[PATCH RFC] mm/hugetlb_cgroup: Add huge_page_order check to avoid incorrectly uncharge

[Wanpeng Li <liwp.linux@gmail.com>]

From: Wanpeng Li <liwp@linux.vnet.ibm.com>

Against linux-next:

Function alloc_huge_page will call hugetlb_cgroup_charge_cgroup
to charge pages, the compound page have less than 3 pages will not
charge to hugetlb cgroup. When alloc_huge_page fails it will call
hugetlb_cgroup_uncharge_cgroup to uncharge pages, however,
hugetlb_cgroup_uncharge_cgroup doesn't have huge_page_order check.
That means it will uncharge pages even if the compound page have less
than 3 pages. Add huge_page_order check to avoid this incorrectly
uncharge.

Signed-off-by: Wanpeng Li <liwp.linux@gmail.com>
---
 mm/hugetlb_cgroup.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index b834e8d..2b9e214 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -252,6 +252,9 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
 
 	if (hugetlb_cgroup_disabled() || !h_cg)
 		return;
+
+	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
+		return;
 
 	res_counter_uncharge(&h_cg->hugepage[idx], csize);
 	return;
-- 
1.7.5.4

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