Refactor cgroups file locations

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

pkg/cgroups/cgroups.go

@@ -1,14 +1,7 @@
 package cgroups
 
 import (
-	"bufio"
 	"errors"
-	"github.com/dotcloud/docker/pkg/mount"
-	"io"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"strings"
 )
 
 var (
@@ -32,68 +25,7 @@ type ActiveCgroup interface {
 	Cleanup() error
 }
 
-// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
-func FindCgroupMountpoint(subsystem string) (string, error) {
-	mounts, err := mount.GetMounts()
-	if err != nil {
-		return "", err
-	}
-
-	for _, mount := range mounts {
-		if mount.Fstype == "cgroup" {
-			for _, opt := range strings.Split(mount.VfsOpts, ",") {
-				if opt == subsystem {
-					return mount.Mountpoint, nil
-				}
-			}
-		}
-	}
-	return "", ErrNotFound
-}
-
-// Returns the relative path to the cgroup docker is running in.
-func GetThisCgroupDir(subsystem string) (string, error) {
-	f, err := os.Open("/proc/self/cgroup")
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()
-
-	return parseCgroupFile(subsystem, f)
-}
-
-func GetInitCgroupDir(subsystem string) (string, error) {
-	f, err := os.Open("/proc/1/cgroup")
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()
-
-	return parseCgroupFile(subsystem, f)
-}
-
-func parseCgroupFile(subsystem string, r io.Reader) (string, error) {
-	s := bufio.NewScanner(r)
-	for s.Scan() {
-		if err := s.Err(); err != nil {
-			return "", err
-		}
-		text := s.Text()
-		parts := strings.Split(text, ":")
-		for _, subs := range strings.Split(parts[1], ",") {
-			if subs == subsystem {
-				return parts[2], nil
-			}
-		}
-	}
-	return "", ErrNotFound
-}
-
-func writeFile(dir, file, data string) error {
-	return ioutil.WriteFile(filepath.Join(dir, file), []byte(data), 0700)
-}
-
-func (c *Cgroup) Apply(pid int) (ActiveCgroup, error) {
+func Apply(c *Cgroup, pid int) (ActiveCgroup, error) {
 	// We have two implementation of cgroups support, one is based on
 	// systemd and the dbus api, and one is based on raw cgroup fs operations
 	// following the pre-single-writer model docs at:

pkg/cgroups/utils.go

@@ -0,0 +1,73 @@
+package cgroups
+
+import (
+	"bufio"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/dotcloud/docker/pkg/mount"
+)
+
+// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
+func FindCgroupMountpoint(subsystem string) (string, error) {
+	mounts, err := mount.GetMounts()
+	if err != nil {
+		return "", err
+	}
+
+	for _, mount := range mounts {
+		if mount.Fstype == "cgroup" {
+			for _, opt := range strings.Split(mount.VfsOpts, ",") {
+				if opt == subsystem {
+					return mount.Mountpoint, nil
+				}
+			}
+		}
+	}
+	return "", ErrNotFound
+}
+
+// Returns the relative path to the cgroup docker is running in.
+func GetThisCgroupDir(subsystem string) (string, error) {
+	f, err := os.Open("/proc/self/cgroup")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	return parseCgroupFile(subsystem, f)
+}
+
+func GetInitCgroupDir(subsystem string) (string, error) {
+	f, err := os.Open("/proc/1/cgroup")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	return parseCgroupFile(subsystem, f)
+}
+
+func parseCgroupFile(subsystem string, r io.Reader) (string, error) {
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return "", err
+		}
+		text := s.Text()
+		parts := strings.Split(text, ":")
+		for _, subs := range strings.Split(parts[1], ",") {
+			if subs == subsystem {
+				return parts[2], nil
+			}
+		}
+	}
+	return "", ErrNotFound
+}
+
+func writeFile(dir, file, data string) error {
+	return ioutil.WriteFile(filepath.Join(dir, file), []byte(data), 0700)
+}

pkg/libcontainer/nsinit/exec.go

@@ -99,7 +99,7 @@ func (ns *linuxNs) Exec(container *libcontainer.Container, term Terminal, args [
 
 func (ns *linuxNs) SetupCgroups(container *libcontainer.Container, nspid int) (cgroups.ActiveCgroup, error) {
 	if container.Cgroups != nil {
-		return container.Cgroups.Apply(nspid)
+		return cgroups.Apply(container.Cgroups, nspid)
 	}
 	return nil, nil
 }