Cleanup systemd apply

libcontainer/cgroups/systemd/apply_systemd.go

@@ -236,53 +236,7 @@ func (m *Manager) Apply(pid int) error {
 		return err
 	}
 
-	if err := joinDevices(c, pid); err != nil {
-		return err
-	}
-
-	// TODO: CpuQuota and CpuPeriod not available in systemd
-	// we need to manually join the cpu.cfs_quota_us and cpu.cfs_period_us
-	if err := joinCpu(c, pid); err != nil {
-		return err
-	}
-
-	// TODO: MemoryReservation and MemorySwap not available in systemd
-	if err := joinMemory(c, pid); err != nil {
-		return err
-	}
-
-	// we need to manually join the freezer, net_cls, net_prio, pids and cpuset cgroup in systemd
-	// because it does not currently support it via the dbus api.
-	if err := joinFreezer(c, pid); err != nil {
-		return err
-	}
-
-	if err := joinNetPrio(c, pid); err != nil {
-		return err
-	}
-	if err := joinNetCls(c, pid); err != nil {
-		return err
-	}
-
-	if err := joinPids(c, pid); err != nil {
-		return err
-	}
-
-	if err := joinCpuset(c, pid); err != nil {
-		return err
-	}
-
-	if err := joinHugetlb(c, pid); err != nil {
-		return err
-	}
-
-	if err := joinPerfEvent(c, pid); err != nil {
-		return err
-	}
-	// FIXME: Systemd does have `BlockIODeviceWeight` property, but we got problem
-	// using that (at least on systemd 208, see https://github.com/opencontainers/runc/libcontainer/pull/354),
-	// so use fs work around for now.
-	if err := joinBlkio(c, pid); err != nil {
+	if err := joinCgroups(c, pid); err != nil {
 		return err
 	}
 
@@ -347,43 +301,41 @@ func join(c *configs.Cgroup, subsystem string, pid int) (string, error) {
 	return path, nil
 }
 
-func joinCpu(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "cpu", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}
-
-func joinFreezer(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "freezer", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}
-
-func joinNetPrio(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "net_prio", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}
-
-func joinNetCls(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "net_cls", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
+func joinCgroups(c *configs.Cgroup, pid int) error {
+	for _, sys := range subsystems {
+		name := sys.Name()
+		switch name {
+		case "name=systemd":
+			// let systemd handle this
+			break
+		case "cpuset":
+			path, err := getSubsystemPath(c, name)
+			if err != nil && !cgroups.IsNotFound(err) {
+				return err
+			}
+			s := &fs.CpusetGroup{}
+			if err := s.ApplyDir(path, c, pid); err != nil {
+				return err
+			}
+			break
+		default:
+			_, err := join(c, name, pid)
+			if err != nil {
+				// Even if it's `not found` error, we'll return err
+				// because devices cgroup is hard requirement for
+				// container security.
+				if name == "devices" {
+					return err
+				}
+				// For other subsystems, omit the `not found` error
+				// because they are optional.
+				if !cgroups.IsNotFound(err) {
+					return err
+				}
+			}
+		}
 	}
-	return nil
-}
 
-func joinPids(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "pids", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
 	return nil
 }
 
@@ -519,27 +471,6 @@ func getUnitName(c *configs.Cgroup) string {
 	return fmt.Sprintf("%s-%s.scope", c.ScopePrefix, c.Name)
 }
 
-// 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 available 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.
-func joinDevices(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "devices", pid)
-	// Even if it's `not found` error, we'll return err because devices cgroup
-	// is hard requirement for container security.
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
 func setKernelMemory(c *configs.Cgroup) error {
 	path, err := getSubsystemPath(c, "memory")
 	if err != nil && !cgroups.IsNotFound(err) {
@@ -554,52 +485,3 @@ func setKernelMemory(c *configs.Cgroup) error {
 	s := &fs.MemoryGroup{}
 	return s.SetKernelMemory(path, c)
 }
-
-func joinMemory(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "memory", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}
-
-// systemd does not atm set up the cpuset controller, so we must manually
-// join it. Additionally that is a very finicky controller where each
-// level must have a full setup as the default for a new directory is "no cpus"
-func joinCpuset(c *configs.Cgroup, pid int) error {
-	path, err := getSubsystemPath(c, "cpuset")
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-
-	s := &fs.CpusetGroup{}
-
-	return s.ApplyDir(path, c, pid)
-}
-
-// `BlockIODeviceWeight` property of systemd does not work properly, and systemd
-// expects device path instead of major minor numbers, which is also confusing
-// for users. So we use fs work around for now.
-func joinBlkio(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "blkio", pid)
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
-func joinHugetlb(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "hugetlb", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}
-
-func joinPerfEvent(c *configs.Cgroup, pid int) error {
-	_, err := join(c, "perf_event", pid)
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
-}