func (raw *data) parent(subsystem string) (string, error) {
	initPath, err := cgroups.GetInitCgroupDir(subsystem)
	if err != nil {
		return "", err
	}
	return filepath.Join(raw.root, subsystem, initPath), nil
}

func getPath(id, driver, subsystem string) (string, error) {
	cgroupRoot, err := cgroups.FindCgroupMountpoint("cpu")
	if err != nil {
		return "", err
	}

	cgroupRoot = filepath.Dir(cgroupRoot)
	if _, err := os.Stat(cgroupRoot); err != nil {
		return "", fmt.Errorf("cgroups fs not found")
	}

	group, err := findGroup(subsystem)
	if err != nil {
		return "", err
	}

	initPath, err := cgroups.GetInitCgroupDir(group)
	if err != nil {
		return "", err
	}

	path := path.Join(cgroupRoot, group, initPath, driver, id, subsystem)
	if _, err := os.Stat(path); err != nil {
		return "", fmt.Errorf("%s not found", path)
	}
	return path, nil
}

func getFreezerPath(c *cgroups.Cgroup) (string, error) {
	mountpoint, err := cgroups.FindCgroupMountpoint("freezer")
	if err != nil {
		return "", err
	}

	initPath, err := cgroups.GetInitCgroupDir("freezer")
	if err != nil {
		return "", err
	}

	return filepath.Join(mountpoint, initPath, fmt.Sprintf("%s-%s", c.Parent, c.Name)), nil

}

func getSubsystemPath(c *configs.Cgroup, subsystem string) (string, error) {
	mountpoint, err := cgroups.FindCgroupMountpoint(subsystem)
	if err != nil {
		return "", err
	}

	initPath, err := cgroups.GetInitCgroupDir(subsystem)
	if err != nil {
		return "", err
	}

	slice := "system.slice"
	if c.Slice != "" {
		slice = c.Slice
	}

	return filepath.Join(mountpoint, initPath, slice, getUnitName(c)), nil
}

func Apply(c *cgroups.Cgroup, pid int) (cgroups.ActiveCgroup, error) {
	var (
		unitName   = getUnitName(c)
		slice      = "system.slice"
		properties []systemd1.Property
		cpuArgs    []cgroupArg
		cpusetArgs []cgroupArg
		memoryArgs []cgroupArg
		res        systemdCgroup
	)

	// First set up things not supported by systemd

	// -1 disables memorySwap
	if c.MemorySwap >= 0 && (c.Memory != 0 || c.MemorySwap > 0) {
		memorySwap := c.MemorySwap

		if memorySwap == 0 {
			// By default, MemorySwap is set to twice the size of RAM.
			memorySwap = c.Memory * 2
		}

		memoryArgs = append(memoryArgs, cgroupArg{"memory.memsw.limit_in_bytes", strconv.FormatInt(memorySwap, 10)})
	}

	if c.CpusetCpus != "" {
		cpusetArgs = append(cpusetArgs, cgroupArg{"cpuset.cpus", c.CpusetCpus})
	}

	if c.Slice != "" {
		slice = c.Slice
	}

	properties = append(properties,
		systemd1.Property{"Slice", dbus.MakeVariant(slice)},
		systemd1.Property{"Description", dbus.MakeVariant("docker container " + c.Name)},
		systemd1.Property{"PIDs", dbus.MakeVariant([]uint32{uint32(pid)})},
	)

	// Always enable accounting, this gets us the same behaviour as the fs implementation,
	// plus the kernel has some problems with joining the memory cgroup at a later time.
	properties = append(properties,
		systemd1.Property{"MemoryAccounting", dbus.MakeVariant(true)},
		systemd1.Property{"CPUAccounting", dbus.MakeVariant(true)},
		systemd1.Property{"BlockIOAccounting", dbus.MakeVariant(true)})

	if c.Memory != 0 {
		properties = append(properties,
			systemd1.Property{"MemoryLimit", dbus.MakeVariant(uint64(c.Memory))})
	}
	// TODO: MemoryReservation and MemorySwap not available in systemd

	if c.CpuShares != 0 {
		properties = append(properties,
			systemd1.Property{"CPUShares", dbus.MakeVariant(uint64(c.CpuShares))})
	}

	if _, err := theConn.StartTransientUnit(unitName, "replace", properties...); err != nil {
		return nil, err
	}

	// To work around the lack of /dev/pts/* support above we need to manually add these
	// so, ask systemd for the cgroup used
	props, err := theConn.GetUnitTypeProperties(unitName, getIfaceForUnit(unitName))
	if err != nil {
		return nil, err
	}

	cgroup := props["ControlGroup"].(string)

	if !c.AllowAllDevices {
		// Atm we can't use the systemd device support because of two missing things:
		// * Support for wildcards to allow mknod on any device
		// * Support for wildcards to allow /dev/pts support
		//
		// The second is available in more recent systemd as "char-pts", but not in e.g. v208 which is
		// in wide use. When both these are availalable we will be able to switch, but need to keep the old
		// implementation for backwards compat.
		//
		// Note: we can't use systemd to set up the initial limits, and then change the cgroup
		// because systemd will re-write the device settings if it needs to re-apply the cgroup context.
		// This happens at least for v208 when any sibling unit is started.

		mountpoint, err := cgroups.FindCgroupMountpoint("devices")
		if err != nil {
			return nil, err
		}

		initPath, err := cgroups.GetInitCgroupDir("devices")
		if err != nil {
			return nil, err
		}

		dir := filepath.Join(mountpoint, initPath, c.Parent, c.Name)

		res.cleanupDirs = append(res.cleanupDirs, dir)

		if err := os.MkdirAll(dir, 0755); err != nil && !os.IsExist(err) {
			return nil, err
		}
//.........这里部分代码省略.........