From 5f4c5fef66581383ee852b301db67f687663004c Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 3 Sep 2015 19:50:37 +0200
Subject: cgroup: always read the supported controllers from the root cgroup of
 the local container

Otherwise we might end up thinking that we support more controllers than
actually enabled for the container we are running in.
---
 src/basic/cgroup-util.c     | 12 ++++++++++--
 src/test/test-cgroup-util.c | 12 ++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index fe8750d0f3..388bd629ee 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -1981,14 +1981,22 @@ int cg_mask_supported(CGroupMask *ret) {
         if (unified < 0)
                 return unified;
         if (unified > 0) {
-                _cleanup_free_ char *controllers = NULL;
+                _cleanup_free_ char *root = NULL, *controllers = NULL, *path = NULL;
                 const char *c;
 
                 /* In the unified hierarchy we can read the supported
                  * and accessible controllers from a the top-level
                  * cgroup attribute */
 
-                r = read_one_line_file("/sys/fs/cgroup/cgroup.controllers", &controllers);
+                r = cg_get_root_path(&root);
+                if (r < 0)
+                        return r;
+
+                r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, root, "cgroup.controllers", &path);
+                if (r < 0)
+                        return r;
+
+                r = read_one_line_file(path, &controllers);
                 if (r < 0)
                         return r;
 
diff --git a/src/test/test-cgroup-util.c b/src/test/test-cgroup-util.c
index ecc9d70bf4..ff7e45901c 100644
--- a/src/test/test-cgroup-util.c
+++ b/src/test/test-cgroup-util.c
@@ -295,6 +295,17 @@ static void test_shift_path(void) {
         test_shift_path_one("/foobar/waldo", "/fuckfuck", "/foobar/waldo");
 }
 
+static void test_mask_supported(void) {
+
+        CGroupMask m;
+        CGroupController c;
+
+        assert_se(cg_mask_supported(&m) >= 0);
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++)
+                printf("'%s' is supported: %s\n", cgroup_controller_to_string(c), yes_no(m & CGROUP_CONTROLLER_TO_MASK(c)));
+}
+
 int main(void) {
         test_path_decode_unit();
         test_path_get_unit();
@@ -309,6 +320,7 @@ int main(void) {
         test_controller_is_valid();
         test_slice_to_path();
         test_shift_path();
+        test_mask_supported();
 
         return 0;
 }
-- 
cgit v1.2.3-54-g00ecf