Copy parents cpus and mems for cpuset

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

cgroups/fs/apply_raw.go

@@ -103,12 +103,20 @@ func GetStats(c *cgroups.Cgroup, subsystem string, pid int) (map[string]float64,
 	return sys.Stats(d)
 }
 
-func (raw *data) path(subsystem string) (string, error) {
+func (raw *data) parent(subsystem string) (string, error) {
 	initPath, err := cgroups.GetInitCgroupDir(subsystem)
 	if err != nil {
 		return "", err
 	}
-	return filepath.Join(raw.root, subsystem, initPath, raw.cgroup), nil
+	return filepath.Join(raw.root, subsystem, initPath), nil
+}
+
+func (raw *data) path(subsystem string) (string, error) {
+	parent, err := raw.parent(subsystem)
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(parent, raw.cgroup), nil
 }
 
 func (raw *data) join(subsystem string) (string, error) {

cgroups/fs/cpuset.go

@@ -1,7 +1,11 @@
 package fs
 
 import (
+	"bytes"
+	"io/ioutil"
 	"os"
+	"path/filepath"
+	"strconv"
 )
 
 type cpusetGroup struct {
@@ -10,16 +14,19 @@ type cpusetGroup struct {
 func (s *cpusetGroup) Set(d *data) error {
 	// we don't want to join this cgroup unless it is specified
 	if d.c.CpusetCpus != "" {
-		dir, err := d.join("cpuset")
+		dir, err := d.path("cpuset")
-		if err != nil && d.c.CpusetCpus != "" {
+		if err != nil {
+			return err
+		}
+		if err := s.ensureParent(dir); err != nil {
 			return err
 		}
-		defer func() {
-			if err != nil {
-				os.RemoveAll(dir)
-			}
-		}()
 
+		// 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
 		}
@@ -34,3 +41,68 @@ func (s *cpusetGroup) Remove(d *data) error {
 func (s *cpusetGroup) Stats(d *data) (map[string]float64, error) {
 	return nil, ErrNotSupportStat
 }
+
+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
+	}
+	if mems, err = ioutil.ReadFile(filepath.Join(parent, "cpuset.mems")); err != nil {
+		return
+	}
+	return cpus, mems, nil
+}
+
+// ensureParent ensures that the parent directory of current is created
+// with the proper cpus and mems files copied from it's parent if the values
+// are a file with a new line char
+func (s *cpusetGroup) ensureParent(current string) error {
+	parent := filepath.Dir(current)
+
+	if _, err := os.Stat(parent); err != nil {
+		if !os.IsNotExist(err) {
+			return err
+		}
+
+		if err := s.ensureParent(parent); err != nil {
+			return err
+		}
+	}
+
+	if err := os.MkdirAll(current, 0755); err != nil && !os.IsExist(err) {
+		return err
+	}
+	return s.copyIfNeeded(current, parent)
+}
+
+// copyIfNeeded copies the cpuset.cpus and cpuset.mems from the parent
+// directory to the current directory if the file's contents are 0
+func (s *cpusetGroup) copyIfNeeded(current, parent string) error {
+	var (
+		err                      error
+		currentCpus, currentMems []byte
+		parentCpus, parentMems   []byte
+	)
+
+	if currentCpus, currentMems, err = s.getSubsystemSettings(current); err != nil {
+		return err
+	}
+	if parentCpus, parentMems, err = s.getSubsystemSettings(parent); err != nil {
+		return err
+	}
+
+	if s.isEmpty(currentCpus) {
+		if err := writeFile(current, "cpuset.cpus", string(parentCpus)); err != nil {
+			return err
+		}
+	}
+	if s.isEmpty(currentMems) {
+		if err := writeFile(current, "cpuset.mems", string(parentMems)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *cpusetGroup) isEmpty(b []byte) bool {
+	return len(bytes.Trim(b, "\n")) == 0
+}