Merge pull request #143 from vishh/enter_cgroup

Enter cgroups as part of NsEnter

Author: vmarmol

cgroups/cgroups.go

@@ -37,4 +37,5 @@ type Cgroup struct {
 
 type ActiveCgroup interface {
 	Cleanup() error
+	Paths() (map[string]string, error)
 }

cgroups/fs/apply_raw.go

@@ -21,12 +21,16 @@ var (
 		"perf_event": &PerfEventGroup{},
 		"freezer":    &FreezerGroup{},
 	}
+	CgroupProcesses = "cgroup.procs"
 )
 
 type subsystem interface {
-	Set(*data) error
+	// Returns the stats, as 'stats', corresponding to the cgroup under 'path'.
+	GetStats(path string, stats *cgroups.Stats) error
+	// Removes the cgroup represented by 'data'.
 	Remove(*data) error
-	GetStats(string, *cgroups.Stats) error
+	// Creates and joins the cgroup represented by data.
+	Set(*data) error
 }
 
 type data struct {
@@ -149,6 +153,18 @@ func (raw *data) parent(subsystem string) (string, error) {
 	return filepath.Join(raw.root, subsystem, initPath), nil
 }
 
+func (raw *data) Paths() (map[string]string, error) {
+	paths := make(map[string]string)
+	for sysname := range subsystems {
+		path, err := raw.path(sysname)
+		if err != nil {
+			return nil, err
+		}
+		paths[sysname] = path
+	}
+	return paths, nil
+}
+
 func (raw *data) path(subsystem string) (string, error) {
 	// If the cgroup name/path is absolute do not look relative to the cgroup of the init process.
 	if filepath.IsAbs(raw.cgroup) {
@@ -169,7 +185,7 @@ func (raw *data) join(subsystem string) (string, error) {
 	if err := os.MkdirAll(path, 0755); err != nil && !os.IsExist(err) {
 		return "", err
 	}
-	if err := writeFile(path, "cgroup.procs", strconv.Itoa(raw.pid)); err != nil {
+	if err := writeFile(path, CgroupProcesses, strconv.Itoa(raw.pid)); err != nil {
 		return "", err
 	}
 	return path, nil

cgroups/fs/cpuset.go

@@ -20,19 +20,10 @@ func (s *CpusetGroup) Set(d *data) error {
 		if err != nil {
 			return err
 		}
-		if err := s.ensureParent(dir); err != nil {
-			return err
-		}
 
-		// because we are not using d.join we need to place the pid into the procs file
-		// unlike the other subsystems
-		if err := writeFile(dir, "cgroup.procs", strconv.Itoa(d.pid)); err != nil {
-			return err
-		}
-		if err := writeFile(dir, "cpuset.cpus", d.c.CpusetCpus); err != nil {
-			return err
-		}
+		return s.SetDir(dir, d.c.CpusetCpus, d.pid)
 	}
+
 	return nil
 }
 
@@ -44,6 +35,24 @@ func (s *CpusetGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }
 
+func (s *CpusetGroup) SetDir(dir, value string, pid int) error {
+	if err := s.ensureParent(dir); err != nil {
+		return err
+	}
+
+	// because we are not using d.join we need to place the pid into the procs file
+	// unlike the other subsystems
+	if err := writeFile(dir, "cgroup.procs", strconv.Itoa(pid)); err != nil {
+		return err
+	}
+
+	if err := writeFile(dir, "cpuset.cpus", value); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (s *CpusetGroup) getSubsystemSettings(parent string) (cpus []byte, mems []byte, err error) {
 	if cpus, err = ioutil.ReadFile(filepath.Join(parent, "cpuset.cpus")); err != nil {
 		return

cgroups/fs/memory.go

@@ -14,7 +14,7 @@ type MemoryGroup struct {
 
 func (s *MemoryGroup) Set(d *data) error {
 	dir, err := d.join("memory")
-	// only return an error for memory if it was not specified
+	// only return an error for memory if it was specified
 	if err != nil && (d.c.Memory != 0 || d.c.MemoryReservation != 0 || d.c.MemorySwap != 0) {
 		return err
 	}