mm/dynamic_hugetlb: use mem_cgroup_force_empty to reclaim pages

hulk inclusion
category: bugfix
bugzilla: 46904 https://gitee.com/openeuler/kernel/issues/I4Y0XO

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

When all processes in the memory cgroup are finished, some memory may still be
occupied such as file cache. Use mem_cgroup_force_empty to reclaim these pages
that charged in the memory cgroup before merging all pages.
Signed-off-by: NLiu Shixin <liushixin2@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

include/linux/memcontrol.h

@@ -1258,6 +1258,8 @@ static inline bool memcg_has_children(struct mem_cgroup *memcg)
 	return ret;
 }
 
+int mem_cgroup_force_empty(struct mem_cgroup *memcg);
+
 #else /* CONFIG_MEMCG */
 
 #define MEM_CGROUP_ID_SHIFT	0

mm/dynamic_hugetlb.c

@@ -849,6 +849,12 @@ int hugetlb_pool_destroy(struct cgroup *cgrp)
 	if (!hpool || hpool->attach_memcg != memcg)
 		return 0;
 
+	/*
+	 * Even if no process exists in the memory cgroup, some pages may still
+	 * be occupied. Release these pages before merging them.
+	 */
+	mem_cgroup_force_empty(hpool->attach_memcg);
+
 	ret = hugetlb_pool_merge_all_pages(hpool);
 	if (ret)
 		return -ENOMEM;

mm/memcontrol.c

@@ -3407,7 +3407,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
  *
  * Caller is responsible for holding css reference for memcg.
  */
-static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
+int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 {
 	int nr_retries = MAX_RECLAIM_RETRIES;