container: remove Mounts from CgroupSubsystems

This field is only used
 - to check if there are any mounts, i.e. len() == 0;
 - to iterate over the list of mounts in watcher.

In both cases, we can reuse MountPoints without any degradation.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

container/libcontainer/helpers.go

@@ -30,10 +30,6 @@ import (
 )
 
 type CgroupSubsystems struct {
-	// Cgroup subsystem mounts.
-	// e.g.: "/sys/fs/cgroup/cpu" -> ["cpu", "cpuacct"]
-	Mounts []cgroups.Mount
-
 	// Cgroup subsystem to their mount location.
 	// e.g.: "cpu" -> "/sys/fs/cgroup/cpu"
 	MountPoints map[string]string
@@ -99,8 +95,6 @@ func getCgroupSubsystemsHelper(allCgroups []cgroups.Mount, disableCgroups map[st
 	}
 
 	// Trim the mounts to only the subsystems we care about.
-	supportedCgroups := make([]cgroups.Mount, 0, len(allCgroups))
-	recordedMountpoints := make(map[string]struct{}, len(allCgroups))
 	mountPoints := make(map[string]string, len(allCgroups))
 	for _, mount := range allCgroups {
 		for _, subsystem := range mount.Subsystems {
@@ -116,17 +110,11 @@ func getCgroupSubsystemsHelper(allCgroups []cgroups.Mount, disableCgroups map[st
 				klog.V(5).Infof("skipping %s, already using mount at %s", mount.Mountpoint, mountPoints[subsystem])
 				continue
 			}
-			if _, ok := recordedMountpoints[mount.Mountpoint]; !ok {
-				// avoid appending the same mount twice in e.g. `cpu,cpuacct` case
-				supportedCgroups = append(supportedCgroups, mount)
-				recordedMountpoints[mount.Mountpoint] = struct{}{}
-			}
 			mountPoints[subsystem] = mount.Mountpoint
 		}
 	}
 
 	return CgroupSubsystems{
-		Mounts:      supportedCgroups,
 		MountPoints: mountPoints,
 	}, nil
 }

container/libcontainer/helpers_test.go

@@ -15,11 +15,9 @@
 package libcontainer
 
 import (
-	"fmt"
 	"io/ioutil"
 	"path/filepath"
 	"reflect"
-	"sort"
 	"strings"
 	"testing"
 
@@ -44,8 +42,6 @@ func cgroupMountsAt(path string, subsystems []string) []cgroups.Mount {
 }
 
 func TestGetCgroupSubsystems(t *testing.T) {
-	ourSubsystems := []string{"cpu,cpuacct", "devices", "memory", "hugetlb", "cpuset", "blkio", "pids"}
-
 	testCases := []struct {
 		mounts   []cgroups.Mount
 		expected CgroupSubsystems
@@ -69,7 +65,6 @@ func TestGetCgroupSubsystems(t *testing.T) {
 					"hugetlb": "/sys/fs/cgroup/hugetlb",
 					"pids":    "/sys/fs/cgroup/pids",
 				},
-				Mounts: cgroupMountsAt("/sys/fs/cgroup", ourSubsystems),
 			},
 		},
 		{
@@ -87,7 +82,6 @@ func TestGetCgroupSubsystems(t *testing.T) {
 					"hugetlb": "/sys/fs/cgroup/hugetlb",
 					"pids":    "/sys/fs/cgroup/pids",
 				},
-				Mounts: cgroupMountsAt("/sys/fs/cgroup", ourSubsystems),
 			},
 		},
 		{
@@ -97,7 +91,6 @@ func TestGetCgroupSubsystems(t *testing.T) {
 				MountPoints: map[string]string{
 					"cpu": "/sys/fs/cgroup/cpu",
 				},
-				Mounts: cgroupMountsAt("/sys/fs/cgroup", []string{"cpu"}),
 			},
 		},
 	}
@@ -113,23 +106,9 @@ func TestGetCgroupSubsystems(t *testing.T) {
 		if err != nil {
 			t.Fatalf("[case %d] Expected no error, but got %v", i, err)
 		}
-		assertCgroupSubsystemsEqual(t, testCase.expected, subSystems, fmt.Sprintf("[case %d]", i))
-	}
-}
-
-func assertCgroupSubsystemsEqual(t *testing.T, expected, actual CgroupSubsystems, message string) {
-	if !reflect.DeepEqual(expected.MountPoints, actual.MountPoints) {
-		t.Fatalf("%s Expected %v == %v", message, expected.MountPoints, actual.MountPoints)
-	}
-
-	sort.Slice(expected.Mounts, func(i, j int) bool {
-		return expected.Mounts[i].Mountpoint < expected.Mounts[j].Mountpoint
-	})
-	sort.Slice(actual.Mounts, func(i, j int) bool {
-		return actual.Mounts[i].Mountpoint < actual.Mounts[j].Mountpoint
-	})
-	if !reflect.DeepEqual(expected.Mounts, actual.Mounts) {
-		t.Fatalf("%s Expected %v == %v", message, expected.Mounts, actual.Mounts)
+		if !reflect.DeepEqual(testCase.expected.MountPoints, subSystems.MountPoints) {
+			t.Fatalf("[case %d] Expected %v == %v", i, testCase.expected.MountPoints, subSystems.MountPoints)
+		}
 	}
 }
 

container/raw/factory.go

@@ -89,7 +89,7 @@ func Register(machineInfoFactory info.MachineInfoFactory, fsInfo fs.FsInfo, incl
 	if err != nil {
 		return fmt.Errorf("failed to get cgroup subsystems: %v", err)
 	}
-	if len(cgroupSubsystems.Mounts) == 0 {
+	if len(cgroupSubsystems.MountPoints) == 0 {
 		return fmt.Errorf("failed to find supported cgroup mounts for the raw factory")
 	}
 

container/raw/watcher.go

@@ -50,7 +50,7 @@ func NewRawContainerWatcher() (watcher.ContainerWatcher, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to get cgroup subsystems: %v", err)
 	}
-	if len(cgroupSubsystems.Mounts) == 0 {
+	if len(cgroupSubsystems.MountPoints) == 0 {
 		return nil, fmt.Errorf("failed to find supported cgroup mounts for the raw factory")
 	}
 
@@ -196,8 +196,8 @@ func (w *rawContainerWatcher) processEvent(event *inotify.Event, events chan wat
 
 	// Derive the container name from the path name.
 	var containerName string
-	for _, mount := range w.cgroupSubsystems.Mounts {
-		mountLocation := path.Clean(mount.Mountpoint) + "/"
+	for _, mount := range w.cgroupSubsystems.MountPoints {
+		mountLocation := path.Clean(mount) + "/"
 		if strings.HasPrefix(event.Name, mountLocation) {
 			containerName = event.Name[len(mountLocation)-1:]
 			break