Merge pull request #2273 from kolyshkin/v2-untangle

cgroup v2 cleanups

libcontainer/cgroups/systemd/unified_hierarchy.go

@@ -4,7 +4,6 @@ package systemd
 
 import (
 	"bytes"
-	"fmt"
 	"io/ioutil"
 	"math"
 	"os"
@@ -38,14 +37,6 @@ func (m *UnifiedManager) Apply(pid int) error {
 	if c.Paths != nil {
 		paths := make(map[string]string)
 		for name, path := range c.Paths {
-			_, err := getSubsystemPath(m.Cgroups, name)
-			if err != nil {
-				// Don't fail if a cgroup hierarchy was not found, just skip this subsystem
-				if cgroups.IsNotFound(err) {
-					continue
-				}
-				return err
-			}
 			paths[name] = path
 		}
 		m.Paths = paths
@@ -139,12 +130,11 @@ func (m *UnifiedManager) Apply(pid int) error {
 		return err
 	}
 
-	if err := joinCgroupsV2(c, pid); err != nil {
+	path, err := getv2Path(m.Cgroups)
+	if err != nil {
 		return err
 	}
-
-	path, err := getSubsystemPath(m.Cgroups, "")
-	if err != nil {
+	if err := createCgroupsv2Path(path); err != nil {
 		return err
 	}
 	m.Paths = map[string]string{
@@ -197,14 +187,26 @@ func (m *UnifiedManager) GetUnifiedPath() (string, error) {
 	}
 	return unifiedPath, nil
 }
+
+func getv2Path(c *configs.Cgroup) (string, error) {
+	slice := "system.slice"
+	if c.Parent != "" {
+		slice = c.Parent
+	}
+
+	slice, err := ExpandSlice(slice)
+	if err != nil {
+		return "", err
+	}
+
+	return filepath.Join(fs2.UnifiedMountpoint, slice, getUnitName(c)), nil
+}
+
 func createCgroupsv2Path(path string) (Err error) {
 	content, err := ioutil.ReadFile("/sys/fs/cgroup/cgroup.controllers")
 	if err != nil {
 		return err
 	}
-	if !filepath.HasPrefix(path, "/sys/fs/cgroup") {
-		return fmt.Errorf("invalid cgroup path %s", path)
-	}
 
 	ctrs := bytes.Fields(content)
 	res := append([]byte("+"), bytes.Join(ctrs, []byte(" +"))...)
@@ -236,14 +238,6 @@ func createCgroupsv2Path(path string) (Err error) {
 	return nil
 }
 
-func joinCgroupsV2(c *configs.Cgroup, pid int) error {
-	path, err := getSubsystemPath(c, "memory")
-	if err != nil {
-		return err
-	}
-	return createCgroupsv2Path(path)
-}
-
 func (m *UnifiedManager) fsManager() (cgroups.Manager, error) {
 	path, err := m.GetUnifiedPath()
 	if err != nil {

libcontainer/cgroups/utils.go

@@ -4,6 +4,7 @@ package cgroups
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -28,6 +29,8 @@ const (
 var (
 	isUnifiedOnce sync.Once
 	isUnified     bool
+
+	errUnified = errors.New("not implemented for cgroup v2 unified hierarchy")
 )
 
 // HugePageSizeUnitList is a list of the units used by the linux kernel when
@@ -307,6 +310,9 @@ func GetAllSubsystems() ([]string, error) {
 
 // GetOwnCgroup returns the relative path to the cgroup docker is running in.
 func GetOwnCgroup(subsystem string) (string, error) {
+	if IsCgroup2UnifiedMode() {
+		return "", errUnified
+	}
 	cgroups, err := ParseCgroupFile("/proc/self/cgroup")
 	if err != nil {
 		return "", err
@@ -325,6 +331,9 @@ func GetOwnCgroupPath(subsystem string) (string, error) {
 }
 
 func GetInitCgroup(subsystem string) (string, error) {
+	if IsCgroup2UnifiedMode() {
+		return "", errUnified
+	}
 	cgroups, err := ParseCgroupFile("/proc/1/cgroup")
 	if err != nil {
 		return "", err