Initial checkin from CRI-O repo

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

vendor/github.com/containerd/cgroups/paths.go

@@ -0,0 +1,88 @@
+package cgroups
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/pkg/errors"
+)
+
+type Path func(subsystem Name) (string, error)
+
+func RootPath(subsysem Name) (string, error) {
+	return "/", nil
+}
+
+// StaticPath returns a static path to use for all cgroups
+func StaticPath(path string) Path {
+	return func(_ Name) (string, error) {
+		return path, nil
+	}
+}
+
+// NestedPath will nest the cgroups based on the calling processes cgroup
+// placing its child processes inside its own path
+func NestedPath(suffix string) Path {
+	paths, err := parseCgroupFile("/proc/self/cgroup")
+	if err != nil {
+		return errorPath(err)
+	}
+	return existingPath(paths, suffix)
+}
+
+// PidPath will return the correct cgroup paths for an existing process running inside a cgroup
+// This is commonly used for the Load function to restore an existing container
+func PidPath(pid int) Path {
+	p := fmt.Sprintf("/proc/%d/cgroup", pid)
+	paths, err := parseCgroupFile(p)
+	if err != nil {
+		return errorPath(errors.Wrapf(err, "parse cgroup file %s", p))
+	}
+	return existingPath(paths, "")
+}
+
+func existingPath(paths map[string]string, suffix string) Path {
+	// localize the paths based on the root mount dest for nested cgroups
+	for n, p := range paths {
+		dest, err := getCgroupDestination(string(n))
+		if err != nil {
+			return errorPath(err)
+		}
+		rel, err := filepath.Rel(dest, p)
+		if err != nil {
+			return errorPath(err)
+		}
+		if rel == "." {
+			rel = dest
+		}
+		paths[n] = filepath.Join("/", rel)
+	}
+	return func(name Name) (string, error) {
+		root, ok := paths[string(name)]
+		if !ok {
+			if root, ok = paths[fmt.Sprintf("name=%s", name)]; !ok {
+				return "", fmt.Errorf("unable to find %q in controller set", name)
+			}
+		}
+		if suffix != "" {
+			return filepath.Join(root, suffix), nil
+		}
+		return root, nil
+	}
+}
+
+func subPath(path Path, subName string) Path {
+	return func(name Name) (string, error) {
+		p, err := path(name)
+		if err != nil {
+			return "", err
+		}
+		return filepath.Join(p, subName), nil
+	}
+}
+
+func errorPath(err error) Path {
+	return func(_ Name) (string, error) {
+		return "", err
+	}
+}