cri: support blockio class in pod and container annotations

This patch adds support for a container annotation and two separate
pod annotations for controlling the blockio class of containers.

The container annotation can be used by a CRI client:
  "io.kubernetes.cri.blockio-class"

Pod annotations specify the blockio class in the K8s pod spec level:
  "blockio.resources.beta.kubernetes.io/pod"
  (pod-wide default for all containers within)

  "blockio.resources.beta.kubernetes.io/container.<container_name>"
  (container-specific overrides)

Correspondingly, this patch adds support for --blockio-class and
--blockio-config-file to ctr, too.

This implementation follows the resource class annotation pattern
introduced in RDT and merged in commit 893701220.

Signed-off-by: Antti Kervinen <antti.kervinen@intel.com>

vendor/github.com/intel/goresctrl/pkg/cgroups/cgrouppath.go

@@ -0,0 +1,75 @@
+// Copyright 2020 Intel Corporation. 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 cgroups
+
+import (
+	"path"
+	"path/filepath"
+)
+
+//nolint
+const (
+	// Tasks is a cgroup's "tasks" entry.
+	Tasks = "tasks"
+	// Procs is cgroup's "cgroup.procs" entry.
+	Procs = "cgroup.procs"
+	// CpuShares is the cpu controller's "cpu.shares" entry.
+	CpuShares = "cpu.shares"
+	// CpuPeriod is the cpu controller's "cpu.cfs_period_us" entry.
+	CpuPeriod = "cpu.cfs_period_us"
+	// CpuQuota is the cpu controller's "cpu.cfs_quota_us" entry.
+	CpuQuota = "cpu.cfs_quota_us"
+	// CpusetCpus is the cpuset controller's cpuset.cpus entry.
+	CpusetCpus = "cpuset.cpus"
+	// CpusetMems is the cpuset controller's cpuset.mems entry.
+	CpusetMems = "cpuset.mems"
+)
+
+var (
+	// mount is the parent directory for per-controller cgroupfs mounts.
+	mountDir = "/sys/fs/cgroup"
+	// v2Dir is the parent directory for per-controller cgroupfs mounts.
+	v2Dir = path.Join(mountDir, "unified")
+	// KubeletRoot is the --cgroup-root option the kubelet is running with.
+	KubeletRoot = ""
+)
+
+// GetMountDir returns the common mount point for cgroup v1 controllers.
+func GetMountDir() string {
+	return mountDir
+}
+
+// SetMountDir sets the common mount point for the cgroup v1 controllers.
+func SetMountDir(dir string) {
+	v2, _ := filepath.Rel(mountDir, v2Dir)
+	mountDir = dir
+	if v2 != "" {
+		v2Dir = path.Join(mountDir, v2)
+	}
+}
+
+// GetV2Dir returns the cgroup v2 unified mount directory.
+func GetV2Dir() string {
+	return v2Dir
+}
+
+// SetV2Dir sets the unified cgroup v2 mount directory.
+func SetV2Dir(dir string) {
+	if dir[0] == '/' {
+		v2Dir = dir
+	} else {
+		v2Dir = path.Join(mountDir, v2Dir)
+	}
+}