cgroup2: split fs2 from fs

split fs2 package from fs, as mixing up fs and fs2 is very likely to result in
unmaintainable code.

Inspired by containerd/cgroups#109

Fix #2157

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

libcontainer/cgroups/fs2/cpu.go

@@ -0,0 +1,56 @@
+// +build linux
+
+package fs2
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"strconv"
+
+	"github.com/opencontainers/runc/libcontainer/cgroups"
+	"github.com/opencontainers/runc/libcontainer/cgroups/fscommon"
+	"github.com/opencontainers/runc/libcontainer/configs"
+)
+
+func setCpu(dirPath string, cgroup *configs.Cgroup) error {
+	if cgroup.Resources.CpuWeight != 0 {
+		if err := fscommon.WriteFile(dirPath, "cpu.weight", strconv.FormatUint(cgroup.Resources.CpuWeight, 10)); err != nil {
+			return err
+		}
+	}
+
+	if cgroup.Resources.CpuMax != "" {
+		if err := fscommon.WriteFile(dirPath, "cpu.max", cgroup.Resources.CpuMax); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+func statCpu(dirPath string, stats *cgroups.Stats) error {
+	f, err := os.Open(filepath.Join(dirPath, "cpu.stat"))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		t, v, err := fscommon.GetCgroupParamKeyValue(sc.Text())
+		if err != nil {
+			return err
+		}
+		switch t {
+		case "usage_usec":
+			stats.CpuStats.CpuUsage.TotalUsage = v * 1000
+
+		case "user_usec":
+			stats.CpuStats.CpuUsage.UsageInUsermode = v * 1000
+
+		case "system_usec":
+			stats.CpuStats.CpuUsage.UsageInKernelmode = v * 1000
+		}
+	}
+	return nil
+}