Make sure to show debian warning also for cgroup 2

Move check to function, to cut down on complexity

pkg/drivers/kic/oci/cgroups_linux.go

@@ -0,0 +1,34 @@
+// +build linux
+
+/*
+Copyright 2021 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package oci
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// IsCgroup2UnifiedMode returns whether we are running in cgroup 2 cgroup2 mode.
+func IsCgroup2UnifiedMode() (bool, error) {
+	var st syscall.Statfs_t
+	if err := syscall.Statfs("/sys/fs/cgroup", &st); err != nil {
+		return false, err
+	}
+	return st.Type == unix.CGROUP2_SUPER_MAGIC, nil
+}

pkg/drivers/kic/oci/cgroups_other.go

@@ -0,0 +1,30 @@
+// +build !linux
+
+/*
+Copyright 2021 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package oci
+
+import (
+	"runtime"
+
+	"github.com/pkg/errors"
+)
+
+// IsCgroup2UnifiedMode returns whether we are running in cgroup 2 cgroup2 mode.
+func IsCgroup2UnifiedMode() (bool, error) {
+	return false, errors.Errorf("Not supported on %s", runtime.GOOS)
+}

pkg/drivers/kic/oci/oci.go

@@ -107,6 +107,24 @@ func PrepareContainerNode(p CreateParams) error {
 	return nil
 }
 
+func hasMemorySwapCgroup() bool {
+	memcgSwap := true
+	if runtime.GOOS == "linux" {
+		var memoryswap string
+		if cgroup2, err := IsCgroup2UnifiedMode(); err == nil && cgroup2 {
+			memoryswap = "/sys/fs/cgroup/memory/memory.swap.max"
+		} else {
+			memoryswap = "/sys/fs/cgroup/memory/memsw.limit_in_bytes"
+		}
+		if _, err := os.Stat(memoryswap); os.IsNotExist(err) {
+			// requires CONFIG_MEMCG_SWAP_ENABLED or cgroup_enable=memory in grub
+			klog.Warning("Your kernel does not support swap limit capabilities or the cgroup is not mounted.")
+			memcgSwap = false
+		}
+	}
+	return memcgSwap
+}
+
 // CreateContainerNode creates a new container node
 func CreateContainerNode(p CreateParams) error {
 	// on windows os, if docker desktop is using Windows Containers. Exit early with error
@@ -152,14 +170,7 @@ func CreateContainerNode(p CreateParams) error {
 		runArgs = append(runArgs, "--ip", p.IP)
 	}
 
-	memcgSwap := true
-	if runtime.GOOS == "linux" {
-		if _, err := os.Stat("/sys/fs/cgroup/memory/memsw.limit_in_bytes"); os.IsNotExist(err) {
-			// requires CONFIG_MEMCG_SWAP_ENABLED or cgroup_enable=memory in grub
-			klog.Warning("Your kernel does not support swap limit capabilities or the cgroup is not mounted.")
-			memcgSwap = false
-		}
-	}
+	memcgSwap := hasMemorySwapCgroup()
 
 	// https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface/
 	var virtualization string