podman cgroup enhancement

currently, setting any sort of resource limit in a pod does nothing. With the newly refactored creation process in c/common, podman ca now set resources at a pod level
meaning that resource related flags can now be exposed to podman pod create.

cgroupfs and systemd are both supported with varying completion. cgroupfs is a much simpler process and one that is virtually complete for all resource types, the flags now just need to be added. systemd on the other hand
has to be handeled via the dbus api meaning that the limits need to be passed as recognized properties to systemd. The properties added so far are the ones that podman pod create supports as well as `cpuset-mems` as this will
be the next flag I work on.

Signed-off-by: Charlie Doern <cdoern@redhat.com>

vendor/github.com/containers/common/pkg/cgroups/utils.go

@@ -0,0 +1,176 @@
+package cgroups
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+var TestMode bool
+
+func cleanString(s string) string {
+	return strings.Trim(s, "\n")
+}
+
+func readAcct(ctr *CgroupControl, name string) (uint64, error) {
+	p := filepath.Join(ctr.getCgroupv1Path(CPUAcct), name)
+	return readFileAsUint64(p)
+}
+
+func readAcctList(ctr *CgroupControl, name string) ([]uint64, error) {
+	p := filepath.Join(ctr.getCgroupv1Path(CPUAcct), name)
+	data, err := ioutil.ReadFile(p)
+	if err != nil {
+		return nil, errors.Wrapf(err, "reading %s", p)
+	}
+	r := []uint64{}
+	for _, s := range strings.Split(string(data), " ") {
+		s = cleanString(s)
+		if s == "" {
+			break
+		}
+		v, err := strconv.ParseUint(s, 10, 64)
+		if err != nil {
+			return nil, errors.Wrapf(err, "parsing %s", s)
+		}
+		r = append(r, v)
+	}
+	return r, nil
+}
+
+// GetSystemCPUUsage returns the system usage for all the cgroups
+func GetSystemCPUUsage() (uint64, error) {
+	cgroupv2, err := IsCgroup2UnifiedMode()
+	if err != nil {
+		return 0, err
+	}
+	if !cgroupv2 {
+		p := filepath.Join(cgroupRoot, CPUAcct, "cpuacct.usage")
+		return readFileAsUint64(p)
+	}
+
+	files, err := ioutil.ReadDir(cgroupRoot)
+	if err != nil {
+		return 0, err
+	}
+	var total uint64
+	for _, file := range files {
+		if !file.IsDir() {
+			continue
+		}
+		p := filepath.Join(cgroupRoot, file.Name(), "cpu.stat")
+
+		values, err := readCgroup2MapPath(p)
+		if err != nil {
+			return 0, err
+		}
+
+		if val, found := values["usage_usec"]; found {
+			v, err := strconv.ParseUint(cleanString(val[0]), 10, 64)
+			if err != nil {
+				return 0, err
+			}
+			total += v * 1000
+		}
+	}
+	return total, nil
+}
+
+func cpusetCopyFileFromParent(dir, file string, cgroupv2 bool) ([]byte, error) {
+	if dir == cgroupRoot {
+		return nil, fmt.Errorf("could not find parent to initialize cpuset %s", file)
+	}
+	path := filepath.Join(dir, file)
+	parentPath := path
+	if cgroupv2 {
+		parentPath = fmt.Sprintf("%s.effective", parentPath)
+	}
+	data, err := ioutil.ReadFile(parentPath)
+	if err != nil {
+		return nil, errors.Wrapf(err, "open %s", path)
+	}
+	if strings.Trim(string(data), "\n") != "" {
+		return data, nil
+	}
+	data, err = cpusetCopyFileFromParent(filepath.Dir(dir), file, cgroupv2)
+	if err != nil {
+		return nil, err
+	}
+	if err := ioutil.WriteFile(path, data, 0o644); err != nil {
+		return nil, errors.Wrapf(err, "write %s", path)
+	}
+	return data, nil
+}
+
+func cpusetCopyFromParent(path string, cgroupv2 bool) error {
+	for _, file := range []string{"cpuset.cpus", "cpuset.mems"} {
+		if _, err := cpusetCopyFileFromParent(path, file, cgroupv2); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// createCgroupv2Path creates the cgroupv2 path and enables all the available controllers
+func createCgroupv2Path(path string) (deferredError error) {
+	if !strings.HasPrefix(path, cgroupRoot+"/") {
+		return fmt.Errorf("invalid cgroup path %s", path)
+	}
+	content, err := ioutil.ReadFile(cgroupRoot + "/cgroup.controllers")
+	if err != nil {
+		return err
+	}
+	ctrs := bytes.Fields(content)
+	res := append([]byte("+"), bytes.Join(ctrs, []byte(" +"))...)
+
+	current := "/sys/fs"
+	elements := strings.Split(path, "/")
+	for i, e := range elements[3:] {
+		current = filepath.Join(current, e)
+		if i > 0 {
+			if err := os.Mkdir(current, 0o755); err != nil {
+				if !os.IsExist(err) {
+					return err
+				}
+			} else {
+				// If the directory was created, be sure it is not left around on errors.
+				defer func() {
+					if deferredError != nil {
+						os.Remove(current)
+					}
+				}()
+			}
+		}
+		// We enable the controllers for all the path components except the last one.  It is not allowed to add
+		// PIDs if there are already enabled controllers.
+		if i < len(elements[3:])-1 {
+			if err := ioutil.WriteFile(filepath.Join(current, "cgroup.subtree_control"), res, 0o755); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func (c *CgroupControl) createCgroupDirectory(controller string) (bool, error) {
+	cPath := c.getCgroupv1Path(controller)
+	_, err := os.Stat(cPath)
+	if err == nil {
+		return false, nil
+	}
+
+	if !os.IsNotExist(err) {
+		return false, err
+	}
+
+	if err := os.MkdirAll(cPath, 0o755); err != nil {
+		return false, errors.Wrapf(err, "error creating cgroup for %s", controller)
+	}
+	return true, nil
+}