[PATCH] mm/hugetlb: fix set_max_huge_pages() when there are surplus pages

[Jinjiang Tu <tujinjiang@huawei.com>]

In set_max_huge_pages(), min_count should mean the acquired persistent
huge pages, but it contains surplus huge pages. It will leads to failing
to freeing free huge pages for a Node.

Steps to reproduce:
1) create 5 huge pages in Node 0
2) run a program to use all the huge pages
3) create 5 huge pages in Node 1
4) echo 0 > nr_hugepages for Node 1 to free the huge pages

The result:
        Node 0    Node 1
Total     5         5
Free      0         5
Surp      5         5

Fixes: 9a30523066cd ("hugetlb: add per node hstate attributes")
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
---
 mm/hugetlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 163190e89ea1..783faec7360b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3758,7 +3758,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 	 * and won't grow the pool anywhere else. Not until one of the
 	 * sysctls are changed, or the surplus pages go out of use.
 	 */
-	min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
+	min_count = h->resv_huge_pages + persistent_huge_pages(h) - h->free_huge_pages;
 	min_count = max(count, min_count);
 	try_to_free_low(h, min_count, nodes_allowed);
 
-- 
2.43.0