[PATCH] memcg: add mem_cgroup_same_or_subtree helper

[Michal Hocko]

We are checking whether a given two groups are same or at least in the
same subtree of a hierarchy at several places. Let's make a helper for
it to make code easier to read.

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
 mm/memcontrol.c |   29 ++++++++++++++++++-----------
 1 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8180cd9..8dbb9d6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1046,6 +1046,21 @@ void mem_cgroup_move_lists(struct page *page,
 	mem_cgroup_add_lru_list(page, to);
 }
 
+/*
+ * Checks whether given mem is same or in the root_mem's
+ * hierarchy subtree
+ */
+static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_mem,
+		struct mem_cgroup *mem)
+{
+	if (root_mem != mem) {
+		return (root_mem->use_hierarchy &&
+			css_is_ancestor(&mem->css, &root_mem->css));
+	}
+
+	return true;
+}
+
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
 {
 	int ret;
@@ -1065,10 +1080,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
 	 * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
 	 * hierarchy(even if use_hierarchy is disabled in "mem").
 	 */
-	if (mem->use_hierarchy)
-		ret = css_is_ancestor(&curr->css, &mem->css);
-	else
-		ret = (curr == mem);
+	ret = mem_cgroup_same_or_subtree(mem, curr);
 	css_put(&curr->css);
 	return ret;
 }
@@ -2150,13 +2162,8 @@ static void drain_all_stock(struct mem_cgroup *root_mem, bool sync)
 		mem = stock->cached;
 		if (!mem || !stock->nr_pages)
 			continue;
-		if (mem != root_mem) {
-			if (!root_mem->use_hierarchy)
-				continue;
-			/* check whether "mem" is under tree of "root_mem" */
-			if (!css_is_ancestor(&mem->css, &root_mem->css))
-				continue;
-		}
+		if (!mem_cgroup_same_or_subtree(root_mem, mem))
+			continue;
 		if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
 			schedule_work_on(cpu, &stock->work);
 	}
-- 
1.7.5.4


-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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