Support cgroup v2

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

go.mod

@@ -64,6 +64,7 @@ require (
 	github.com/NYTimes/gziphandler v1.1.1 // indirect
 	github.com/Nvveen/Gotty v0.0.0-20120604004816-cd527374f1e5 // indirect
 	github.com/bronze1man/goStrongswanVici v0.0.0-20190828090544-27d02f80ba40 // indirect
+	github.com/containerd/cgroups v0.0.0-20200710171044-318312a37340
 	github.com/containerd/containerd v1.4.1
 	github.com/containerd/cri v1.11.1-0.20200820101445-b0cc07999aa5
 	github.com/coreos/flannel v0.12.0

pkg/agent/run.go

@@ -3,12 +3,15 @@ package agent
 import (
 	"context"
 	"errors"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
 	"time"
 
+	"github.com/containerd/cgroups"
+	cgroupsv2 "github.com/containerd/cgroups/v2"
 	systemd "github.com/coreos/go-systemd/daemon"
 	"github.com/rancher/k3s/pkg/agent/config"
 	"github.com/rancher/k3s/pkg/agent/containerd"
@@ -170,6 +173,13 @@ func Run(ctx context.Context, cfg cmds.Agent) error {
 }
 
 func validate() error {
+	if cgroups.Mode() == cgroups.Unified {
+		return validateCgroupsV2()
+	}
+	return validateCgroupsV1()
+}
+
+func validateCgroupsV1() error {
 	cgroups, err := ioutil.ReadFile("/proc/self/cgroup")
 	if err != nil {
 		return err
@@ -188,6 +198,27 @@ func validate() error {
 	return nil
 }
 
+func validateCgroupsV2() error {
+	manager, err := cgroupsv2.LoadManager("/sys/fs/cgroup", "/")
+	if err != nil {
+		return err
+	}
+	controllers, err := manager.RootControllers()
+	if err != nil {
+		return err
+	}
+	m := make(map[string]struct{})
+	for _, controller := range controllers {
+		m[controller] = struct{}{}
+	}
+	for _, controller := range []string{"cpu", "cpuset", "memory"} {
+		if _, ok := m[controller]; !ok {
+			return fmt.Errorf("faild to find %s cgroup (v2)", controller)
+		}
+	}
+	return nil
+}
+
 func configureNode(ctx context.Context, agentConfig *daemonconfig.Agent, nodes v1.NodeInterface) error {
 	count := 0
 	for {

vendor/modules.txt

@@ -166,6 +166,7 @@ github.com/cilium/ebpf/internal/unix
 # github.com/container-storage-interface/spec v1.2.0
 github.com/container-storage-interface/spec/lib/go/csi
 # github.com/containerd/cgroups v0.0.0-20200710171044-318312a37340 => github.com/containerd/cgroups v0.0.0-20200531161412-0dbf7f05ba59
+## explicit
 github.com/containerd/cgroups
 github.com/containerd/cgroups/stats/v1
 github.com/containerd/cgroups/v2