[RFC PATCH 9/9 v2] cgroup: avoid allocating rstat when flush func not present

[JP Kobryn <inwardvessel@gmail.com>]

If a given subsystem is not the base type and does not have a flush func, do
not perform any rstat allocation.

Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
---
 kernel/cgroup/rstat.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 03effaaf09a4..4feefa37fa46 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -423,6 +423,9 @@ int cgroup_rstat_init(struct cgroup_subsys_state *css)
 {
 	int cpu;
 
+	if (css->ss && !css->ss->css_rstat_flush)
+		return 0;
+
 	/* the root cgrp css has rstat_cpu preallocated */
 	if (!css->rstat_cpu) {
 		css->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
@@ -445,6 +448,9 @@ void cgroup_rstat_exit(struct cgroup_subsys_state *css)
 {
 	int cpu;
 
+	if (css->ss && !css->ss->css_rstat_flush)
+		return;
+
 	cgroup_rstat_flush(css);
 
 	/* sanity check */
-- 
2.47.1