systemd cgroup driver: Split support for unified cgroup2 hierarchy into its own Manager

libcontainer/cgroups/systemd/apply_systemd.go

@@ -22,7 +22,7 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-type Manager struct {
+type LegacyManager struct {
 	mu      sync.Mutex
 	Cgroups *configs.Cgroup
 	Paths   map[string]string
@@ -167,15 +167,28 @@ func NewSystemdCgroupsManager() (func(config *configs.Cgroup, paths map[string]s
 	if !systemdUtil.IsRunningSystemd() {
 		return nil, fmt.Errorf("systemd not running on this host, can't use systemd as a cgroups.Manager")
 	}
-	return func(config *configs.Cgroup, paths map[string]string) cgroups.Manager {
-		return &Manager{
-			Cgroups: config,
-			Paths:   paths,
-		}
-	}, nil
+	unified, err := IsCgroup2UnifiedMode()
+	if err != nil {
+		return nil, err
+	}
+	if unified {
+		return func(config *configs.Cgroup, paths map[string]string) cgroups.Manager {
+			return &UnifiedManager{
+				Cgroups: config,
+				Paths:   paths,
+			}
+		}, nil
+	} else {
+		return func(config *configs.Cgroup, paths map[string]string) cgroups.Manager {
+			return &LegacyManager{
+				Cgroups: config,
+				Paths:   paths,
+			}
+		}, nil
+	}
 }
 
-func (m *Manager) Apply(pid int) error {
+func (m *LegacyManager) Apply(pid int) error {
 	var (
 		c          = m.Cgroups
 		unitName   = getUnitName(c)
@@ -325,7 +338,7 @@ func (m *Manager) Apply(pid int) error {
 	return nil
 }
 
-func (m *Manager) Destroy() error {
+func (m *LegacyManager) Destroy() error {
 	if m.Cgroups.Paths != nil {
 		return nil
 	}
@@ -339,7 +352,7 @@ func (m *Manager) Destroy() error {
 	return nil
 }
 
-func (m *Manager) GetPaths() map[string]string {
+func (m *LegacyManager) GetPaths() map[string]string {
 	m.mu.Lock()
 	paths := m.Paths
 	m.mu.Unlock()
@@ -456,7 +469,7 @@ func getSubsystemPath(c *configs.Cgroup, subsystem string) (string, error) {
 	return filepath.Join(mountpoint, initPath, slice, getUnitName(c)), nil
 }
 
-func (m *Manager) Freeze(state configs.FreezerState) error {
+func (m *LegacyManager) Freeze(state configs.FreezerState) error {
 	path, err := getSubsystemPath(m.Cgroups, "freezer")
 	if err != nil {
 		return err
@@ -475,23 +488,23 @@ func (m *Manager) Freeze(state configs.FreezerState) error {
 	return nil
 }
 
-func (m *Manager) GetPids() ([]int, error) {
+func (m *LegacyManager) GetPids() ([]int, error) {
 	path, err := getSubsystemPath(m.Cgroups, "devices")
 	if err != nil {
 		return nil, err
 	}
 	return cgroups.GetPids(path)
 }
 
-func (m *Manager) GetAllPids() ([]int, error) {
+func (m *LegacyManager) GetAllPids() ([]int, error) {
 	path, err := getSubsystemPath(m.Cgroups, "devices")
 	if err != nil {
 		return nil, err
 	}
 	return cgroups.GetAllPids(path)
 }
 
-func (m *Manager) GetStats() (*cgroups.Stats, error) {
+func (m *LegacyManager) GetStats() (*cgroups.Stats, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	stats := cgroups.NewStats()
@@ -508,7 +521,7 @@ func (m *Manager) GetStats() (*cgroups.Stats, error) {
 	return stats, nil
 }
 
-func (m *Manager) Set(container *configs.Config) error {
+func (m *LegacyManager) Set(container *configs.Config) error {
 	// If Paths are set, then we are just joining cgroups paths
 	// and there is no need to set any values.
 	if m.Cgroups.Paths != nil {

libcontainer/cgroups/systemd/unified_hierarchy.go

@@ -0,0 +1,62 @@
+// +build linux,!static_build
+
+package systemd
+
+import (
+	"fmt"
+	"syscall"
+
+	"github.com/opencontainers/runc/libcontainer/cgroups"
+	"github.com/opencontainers/runc/libcontainer/configs"
+	"golang.org/x/sys/unix"
+)
+
+// IsCgroup2UnifiedMode returns whether we are running in cgroup v2 unified mode.
+func IsCgroup2UnifiedMode() (bool, error) {
+	var st syscall.Statfs_t
+	if err := syscall.Statfs("/sys/fs/cgroup", &st); err != nil {
+		return false, fmt.Errorf("cannot statfs cgroup root: %v", err)
+	}
+	return st.Type == unix.CGROUP2_SUPER_MAGIC, nil
+}
+
+type UnifiedManager struct {
+	Cgroups *configs.Cgroup
+	Paths   map[string]string
+}
+
+func NewUnifiedSystemdCgroupsManager() (func(config *configs.Cgroup, paths map[string]string) cgroups.Manager, error) {
+	return nil, fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) Apply(pid int) error {
+	return fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) GetPids() ([]int, error) {
+	return nil, fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) GetAllPids() ([]int, error) {
+	return nil, fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) Destroy() error {
+	return fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) GetPaths() map[string]string {
+	return nil
+}
+
+func (m *UnifiedManager) GetStats() (*cgroups.Stats, error) {
+	return nil, fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) Set(container *configs.Config) error {
+	return fmt.Errorf("unified hierarchy not supported")
+}
+
+func (m *UnifiedManager) Freeze(state configs.FreezerState) error {
+	return fmt.Errorf("unified hierarchy not supported")
+}