v2: toggle ancestors of c.path, not c.path itself

cmd/cgctl/main.go

@@ -46,6 +46,7 @@ func main() {
 		newCommand,
 		delCommand,
 		listCommand,
+		listControllersCommand,
 		statCommand,
 	}
 	app.Before = func(clix *cli.Context) error {
@@ -76,7 +77,7 @@ var newCommand = cli.Command{
 			return err
 		}
 		if clix.Bool("enable") {
-			controllers, err := c.ListControllers()
+			controllers, err := c.RootControllers()
 			if err != nil {
 				return err
 			}
@@ -121,6 +122,26 @@ var listCommand = cli.Command{
 	},
 }
 
+var listControllersCommand = cli.Command{
+	Name:  "list-controllers",
+	Usage: "list controllers in a cgroup",
+	Action: func(clix *cli.Context) error {
+		path := clix.Args().First()
+		c, err := v2.LoadManager(clix.GlobalString("mountpoint"), path)
+		if err != nil {
+			return err
+		}
+		controllers, err := c.Controllers()
+		if err != nil {
+			return err
+		}
+		for _, c := range controllers {
+			fmt.Println(c)
+		}
+		return nil
+	},
+}
+
 var statCommand = cli.Command{
 	Name:  "stat",
 	Usage: "stat a cgroup",

v2/manager.go

@@ -168,25 +168,20 @@ func setResources(path string, resources *Resources) error {
 	return nil
 }
 
-func (c *Manager) ListControllers() ([]string, error) {
-	f, err := os.Open(filepath.Join(c.path, controllersFile))
+func (c *Manager) RootControllers() ([]string, error) {
+	b, err := ioutil.ReadFile(filepath.Join(c.unifiedMountpoint, controllersFile))
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	return strings.Fields(string(b)), nil
+}
 
-	var (
-		out []string
-		s   = bufio.NewScanner(f)
-	)
-	s.Split(bufio.ScanWords)
-	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return nil, err
-		}
-		out = append(out, s.Text())
+func (c *Manager) Controllers() ([]string, error) {
+	b, err := ioutil.ReadFile(filepath.Join(c.path, controllersFile))
+	if err != nil {
+		return nil, err
 	}
-	return out, nil
+	return strings.Fields(string(b)), nil
 }
 
 type ControllerToggle int
@@ -205,7 +200,31 @@ func toggleFunc(controllers []string, prefix string) []string {
 }
 
 func (c *Manager) ToggleControllers(controllers []string, t ControllerToggle) error {
-	f, err := os.OpenFile(filepath.Join(c.path, subtreeControl), os.O_WRONLY, 0)
+	// when c.path is like /foo/bar/baz, the following files need to be written:
+	// * /sys/fs/cgroup/cgroup.subtree_control
+	// * /sys/fs/cgroup/foo/cgroup.subtree_control
+	// * /sys/fs/cgroup/foo/bar/cgroup.subtree_control
+	// Note that /sys/fs/cgroup/foo/bar/baz/cgroup.subtree_control does not need to be written.
+	split := strings.Split(c.path, "/")
+	var lastErr error
+	for i, _ := range split {
+		f := strings.Join(split[:i], "/")
+		if !strings.HasPrefix(f, c.unifiedMountpoint) || f == c.path {
+			continue
+		}
+		filePath := filepath.Join(f, subtreeControl)
+		if err := c.writeSubtreeControl(filePath, controllers, t); err != nil {
+			// When running as rootless, the user may face EPERM on parent groups, but it is neglible when the
+			// controller is already written.
+			// So we only return the last error.
+			lastErr = errors.Wrapf(err, "failed to write subtree controllers %+v to %q", controllers, filePath)
+		}
+	}
+	return lastErr
+}
+
+func (c *Manager) writeSubtreeControl(filePath string, controllers []string, t ControllerToggle) error {
+	f, err := os.OpenFile(filePath, os.O_WRONLY, 0)
 	if err != nil {
 		return err
 	}
@@ -283,7 +302,7 @@ var singleValueFiles = []string{
 }
 
 func (c *Manager) Stat() (*stats.Metrics, error) {
-	controllers, err := c.ListControllers()
+	controllers, err := c.Controllers()
 	if err != nil {
 		return nil, err
 	}