Update cgroups paths in state to be a map with cgroup type as key and path as value.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)

cgroups/cgroups.go

@@ -37,5 +37,5 @@ type Cgroup struct {
 
 type ActiveCgroup interface {
 	Cleanup() error
-	Paths() ([]string, error)
+	Paths() (map[string]string, error)
 }

cgroups/fs/apply_raw.go

@@ -153,14 +153,14 @@ func (raw *data) parent(subsystem string) (string, error) {
 	return filepath.Join(raw.root, subsystem, initPath), nil
 }
 
-func (raw *data) Paths() ([]string, error) {
+func (raw *data) Paths() (map[string]string, error) {
-	var paths []string
+	paths := make(map[string]string)
 	for sysname := range subsystems {
 		path, err := raw.path(sysname)
 		if err != nil {
 			return nil, err
 		}
-		paths = append(paths, path)
+		paths[sysname] = path
 	}
 	return paths, nil
 }

cgroups/systemd/apply_systemd.go

@@ -22,6 +22,7 @@ import (
 
 type systemdCgroup struct {
 	cleanupDirs []string
+	cgroup      *cgroups.Cgroup
 }
 
 type subsystem interface {
@@ -100,6 +101,7 @@ func Apply(c *cgroups.Cgroup, pid int) (cgroups.ActiveCgroup, error) {
 		res        systemdCgroup
 	)
 
+	res.cgroup = c
 	// First set up things not supported by systemd
 
 	// -1 disables memorySwap
@@ -320,8 +322,22 @@ func writeFile(dir, file, data string) error {
 	return ioutil.WriteFile(filepath.Join(dir, file), []byte(data), 0700)
 }
 
-func (c *systemdCgroup) Paths() ([]string, error) {
+func (c *systemdCgroup) Paths() (map[string]string, error) {
-	return c.cleanupDirs, nil
+	paths := make(map[string]string)
+	for sysname := range subsystems {
+		subsystemPath, err := getSubsystemPath(c.cgroup, sysname)
+		if err != nil {
+			// Don't fail if a cgroup hierarchy was not found, just skip this subsystem
+			if err == cgroups.ErrNotFound {
+				continue
+			}
+
+			return nil, err
+		}
+		paths[sysname] = subsystemPath
+	}
+
+	return paths, nil
 }
 
 func (c *systemdCgroup) Cleanup() error {

cgroups/utils.go

@@ -175,7 +175,7 @@ func pathExists(path string) bool {
 	return true
 }
 
-func EnterPid(cgroupPaths []string, pid int) error {
+func EnterPid(cgroupPaths map[string]string, pid int) error {
 	for _, path := range cgroupPaths {
 		if pathExists(path) {
 			if err := ioutil.WriteFile(filepath.Join(path, "cgroup.procs"),

state.go

@@ -19,8 +19,8 @@ type State struct {
 	// Network runtime state.
 	NetworkState network.NetworkState `json:"network_state,omitempty"`
 
-	// Path to all the cgroup dirs.
+	// Path to all the cgroups setup for a container. Key is cgroup subsystem name.
-	CgroupPaths []string `json:"cgroup_paths,omitempty"`
+	CgroupPaths map[string]string `json:"cgroup_paths,omitempty"`
 }
 
 // The running state of the container.