Enter cgroups while entering namespaces as part of NsEnter.

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

cgroups/fs/apply_raw.go

@@ -21,12 +21,15 @@ var (
 		"perf_event": &PerfEventGroup{},
 		"freezer":    &FreezerGroup{},
 	}
+	cgroupProcesses = "cgroup.procs"
 )
 
 type subsystem interface {
-	Set(*data) error
-	Remove(*data) error
+	Active(d *data) (bool, error)
+	Enter(string, string) error
 	GetStats(string, *cgroups.Stats) error
+	Remove(*data) error
+	Set(*data) error
 }
 
 type data struct {
@@ -116,6 +119,36 @@ func GetPids(c *cgroups.Cgroup) ([]int, error) {
 	return cgroups.ReadProcsFile(dir)
 }
 
+func EnterPid(c *cgroups.Cgroup, pid int) error {
+	d, err := getCgroupData(c, 0)
+	if err != nil {
+		return err
+	}
+
+	for sysname, sys := range subsystems {
+		active, err := sys.Active(d)
+		if err != nil {
+			return err
+		}
+		if !active {
+			continue
+		}
+		path, err := d.path(sysname)
+		if err != nil {
+			// Don't fail if a cgroup hierarchy was not found, just skip this subsystem
+			if err == cgroups.ErrNotFound {
+				continue
+			}
+			return err
+		}
+		if err := sys.Enter(path, strconv.FormatInt(int64(pid), 10)); err != nil {
+			return err
+		}
+	}
+	
+	return nil
+}
+
 func getCgroupData(c *cgroups.Cgroup, pid int) (*data, error) {
 	// we can pick any subsystem to find the root
 	cgroupRoot, err := cgroups.FindCgroupMountpoint("cpu")

cgroups/fs/blkio.go

@@ -139,3 +139,12 @@ func (s *BlkioGroup) GetStats(path string, stats *cgroups.Stats) error {
 
 	return nil
 }
+
+func (s *BlkioGroup) Active(d *data) (bool, error) {
+	return true, nil
+}
+
+func (s *BlkioGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}
+

cgroups/fs/cpu.go

@@ -70,3 +70,18 @@ func (s *CpuGroup) GetStats(path string, stats *cgroups.Stats) error {
 	}
 	return nil
 }
+
+func (s *CpuGroup) Active(d *data) (bool, error) {
+	dir, err := d.path("cpu")
+	if err != nil {
+		return false, err
+	}
+	if FileExists(dir) {
+		return true, nil
+	}
+	return false, nil
+}
+
+func (s *CpuGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/cpuacct.go

@@ -161,3 +161,11 @@ func getPercpuUsage(path string) ([]uint64, error) {
 	}
 	return percpuUsage, nil
 }
+
+func (s *CpuacctGroup) Active(d *data) (bool, error) {
+	return true, nil
+}
+
+func (s *CpuacctGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/cpuset.go

@@ -108,3 +108,20 @@ func (s *CpusetGroup) copyIfNeeded(current, parent string) error {
 func (s *CpusetGroup) isEmpty(b []byte) bool {
 	return len(bytes.Trim(b, "\n")) == 0
 }
+
+func (s *CpusetGroup) Active(d *data) (bool, error) {
+	if d.c.CpusetCpus != "" {
+		dir, err := d.path("cpuset")
+		if err != nil {
+			return false, err
+		}
+		if FileExists(dir) {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func (s *CpusetGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/devices.go

@@ -32,3 +32,11 @@ func (s *DevicesGroup) Remove(d *data) error {
 func (s *DevicesGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }
+
+func (s *DevicesGroup) Active(d *data) (bool, error) {
+	return true, nil
+}
+
+func (s *DevicesGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/freezer.go

@@ -48,3 +48,12 @@ func (s *FreezerGroup) Remove(d *data) error {
 func (s *FreezerGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }
+
+func (s *FreezerGroup) Active(d *data) (bool, error) {
+	return true, nil
+}
+
+func (s *FreezerGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}
+

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
 	}
@@ -90,3 +90,19 @@ func (s *MemoryGroup) GetStats(path string, stats *cgroups.Stats) error {
 
 	return nil
 }
+
+func (s *MemoryGroup) Active(d *data) (bool, error) {
+	dir, err := d.path("memory")
+	if err != nil {
+		return false, err
+	}
+	if FileExists(dir) {
+		return true, nil
+	}
+	
+	return false, nil
+}
+
+func (s *MemoryGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/perf_event.go

@@ -22,3 +22,11 @@ func (s *PerfEventGroup) Remove(d *data) error {
 func (s *PerfEventGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }
+
+func (s *PerfEventGroup) Active(d *data) (bool, error) {
+	return true, nil
+}
+
+func (s *PerfEventGroup) Enter(path, pid string) error {
+	return writeFile(path, cgroupProcesses, pid)
+}

cgroups/fs/utils.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -38,3 +39,10 @@ func getCgroupParamInt(cgroupPath, cgroupFile string) (uint64, error) {
 	}
 	return strconv.ParseUint(strings.TrimSpace(string(contents)), 10, 64)
 }
+
+func FileExists(path string) bool {
+	if _, err := os.Stat(path); err == nil {
+		return true
+	}
+	return false
+}

namespaces/execin.go

@@ -12,6 +12,7 @@ import (
 	"syscall"
 
 	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/cgroups/fs"
 	"github.com/docker/libcontainer/label"
 	"github.com/docker/libcontainer/syncpipe"
 	"github.com/docker/libcontainer/system"
@@ -21,6 +22,10 @@ import (
 // setns code in a single threaded environment joining the existing containers' namespaces.
 func ExecIn(container *libcontainer.Config, state *libcontainer.State, userArgs []string, initPath, action string,
 	stdin io.Reader, stdout, stderr io.Writer, console string, startCallback func(*exec.Cmd)) (int, error) {
+	// Enter cgroups.
+	if err := EnterCgroups(container); err != nil {
+		return err
+	}
 
 	args := []string{fmt.Sprintf("nsenter-%s", action), "--nspid", strconv.Itoa(state.InitPid)}
 
@@ -102,3 +107,7 @@ func FinalizeSetns(container *libcontainer.Config, args []string) error {
 
 	panic("unreachable")
 }
+
+func EnterCgroups(container *libcontainer.Config) error {
+	return fs.EnterPid(container.Cgroups, os.Getpid())	
+}