Support cgroups v2

Some of our tests are assuming cgroups v1, but our BuildKite hosts are
now using cgroups v2.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

Author: Kazuyoshi Kato

runtime/integ_test.go

@@ -13,6 +13,8 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/firecracker-microvm/firecracker-containerd/internal"
@@ -38,3 +40,15 @@ var testNameToVMIDReplacer = strings.NewReplacer("/", "-", "_", "-")
 func testNameToVMID(s string) string {
 	return testNameToVMIDReplacer.Replace(s)
 }
+
+func cgroupExists(name string) bool {
+	// cgroups v1
+	_, err := os.Stat(filepath.Join("/sys/fs/cgroup/cpu", name))
+	if err == nil {
+		return true
+	}
+
+	// cgroups v2
+	_, err = os.Stat(filepath.Join("/sys/fs/cgroup", name))
+	return err == nil
+}

runtime/jailer_integ_test.go

@@ -140,9 +140,13 @@ func testJailer(t *testing.T, jailerConfig *proto.JailerConfig) {
 	fcClient, err := integtest.NewFCControlClient(integtest.ContainerdSockPath)
 	require.NoError(t, err)
 
-	_, err = fcClient.CreateVM(ctx, &request)
+	resp, err := fcClient.CreateVM(ctx, &request)
 	require.NoError(t, err)
 
+	if jailerConfig != nil {
+		assert.True(t, cgroupExists(resp.CgroupPath))
+	}
+
 	c, err := client.NewContainer(ctx,
 		vmID+"-container",
 		containerd.WithSnapshotter(defaultSnapshotterName),

runtime/service_integ_test.go

@@ -612,9 +612,8 @@ func testMultipleExecs(
 		if err != nil {
 			return err
 		}
-		_, err = os.Stat(filepath.Join("/sys/fs/cgroup/cpu", cgroupPath))
-		if err != nil {
-			return err
+		if !cgroupExists(cgroupPath) {
+			return fmt.Errorf("failed to find %q", cgroupPath)
 		}
 
 		ok, err := regexp.Match(".+/"+vmIDStr, []byte(cgroupPath))