cgroup mount destination: unknown

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// 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 getCgroupDestination(subsystem string) (string, error) { f, err := os.Open("/proc/self/mountinfo") if err != nil { return "", err } defer f.Close() s := bufio.NewScanner(f) for s.Scan() { fields := strings.Split(s.Text(), " ") if len(fields) < 10 { // broken mountinfo? continue } if fields[len(fields)-3] != "cgroup" { continue } for _, opt := range strings.Split(fields[len(fields)-1], ",") { if opt == subsystem { return fields[3], nil } } } if err := s.Err(); err != nil { return "", err } return "", ErrNoCgroupMountDestination } func parseCgroupFile(path string) (map[string]string, error) { f, err := os.Open(path) if err != nil { return nil, err } defer f.Close() return parseCgroupFromReader(f) } func parseCgroupFromReader(r io.Reader) (map[string]string, error) { var ( cgroups = make(map[string]string) s = bufio.NewScanner(r) ) for s.Scan() { if err := s.Err(); err != nil { return nil, err } var ( text = s.Text() parts = strings.SplitN(text, ":", 3) ) if len(parts) < 3 { return nil, fmt.Errorf("invalid cgroup entry: %q", text) } for _, subs := range strings.Split(parts[1], ",") { if subs != "" { cgroups[subs] = parts[2] } } } return cgroups, nil }