storage: create k8s emptyDir inside VM

pkg/katautils/create.go

@@ -161,8 +161,11 @@ func HandleFactory(ctx context.Context, vci vc.VC, runtimeConfig *oci.RuntimeCon
 // of the same pod the already existing volume is reused.
 func SetEphemeralStorageType(ociSpec oci.CompatOCISpec) oci.CompatOCISpec {
 	for idx, mnt := range ociSpec.Mounts {
-		if IsEphemeralStorage(mnt.Source) {
-			ociSpec.Mounts[idx].Type = "ephemeral"
+		if vc.IsEphemeralStorage(mnt.Source) {
+			ociSpec.Mounts[idx].Type = vc.KataEphemeralDevType
+		}
+		if vc.Isk8sHostEmptyDir(mnt.Source) {
+			ociSpec.Mounts[idx].Type = vc.KataLocalDevType
 		}
 	}
 	return ociSpec

pkg/katautils/create_test.go

@@ -190,7 +190,7 @@ func TestSetEphemeralStorageType(t *testing.T) {
 	}
 	defer os.RemoveAll(dir)
 
-	ephePath := filepath.Join(dir, k8sEmptyDir, "tmp-volume")
+	ephePath := filepath.Join(dir, vc.K8sEmptyDir, "tmp-volume")
 	err = os.MkdirAll(ephePath, testDirMode)
 	assert.Nil(err)
 

pkg/katautils/utils.go

@@ -14,12 +14,6 @@ import (
 	"path/filepath"
 	"strings"
 	"syscall"
-
-	vc "github.com/kata-containers/runtime/virtcontainers"
-)
-
-const (
-	k8sEmptyDir = "kubernetes.io~empty-dir"
 )
 
 // FileExists test is a file exiting or not
@@ -31,28 +25,6 @@ func FileExists(path string) bool {
 	return true
 }
 
-// IsEphemeralStorage returns true if the given path
-// to the storage belongs to kubernetes ephemeral storage
-//
-// This method depends on a specific path used by k8s
-// to detect if it's of type ephemeral. As of now,
-// this is a very k8s specific solution that works
-// but in future there should be a better way for this
-// method to determine if the path is for ephemeral
-// volume type
-func IsEphemeralStorage(path string) bool {
-	splitSourceSlice := strings.Split(path, "/")
-	if len(splitSourceSlice) > 1 {
-		storageType := splitSourceSlice[len(splitSourceSlice)-2]
-		if storageType == k8sEmptyDir {
-			if _, fsType, _ := vc.GetDevicePathAndFsType(path); fsType == "tmpfs" {
-				return true
-			}
-		}
-	}
-	return false
-}
-
 // ResolvePath returns the fully resolved and expanded value of the
 // specified path.
 func ResolvePath(path string) (string, error) {

pkg/katautils/utils_test.go

@@ -366,34 +366,3 @@ func TestGetFileContents(t *testing.T) {
 		assert.Equal(t, contents, d.contents)
 	}
 }
-
-func TestIsEphemeralStorage(t *testing.T) {
-	if os.Geteuid() != 0 {
-		t.Skip(testDisabledNeedRoot)
-	}
-
-	dir, err := ioutil.TempDir(testDir, "foo")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(dir)
-
-	sampleEphePath := filepath.Join(dir, k8sEmptyDir, "tmp-volume")
-	err = os.MkdirAll(sampleEphePath, testDirMode)
-	assert.Nil(t, err)
-
-	err = syscall.Mount("tmpfs", sampleEphePath, "tmpfs", 0, "")
-	assert.Nil(t, err)
-	defer syscall.Unmount(sampleEphePath, 0)
-
-	isEphe := IsEphemeralStorage(sampleEphePath)
-	if !isEphe {
-		t.Fatalf("Unable to correctly determine volume type")
-	}
-
-	sampleEphePath = "/var/lib/kubelet/pods/366c3a75-4869-11e8-b479-507b9ddd5ce4/volumes/cache-volume"
-	isEphe = IsEphemeralStorage(sampleEphePath)
-	if isEphe {
-		t.Fatalf("Unable to correctly determine volume type")
-	}
-}

virtcontainers/container.go

@@ -477,7 +477,13 @@ func (c *Container) mountSharedDirMounts(hostSharedDir, guestSharedDir string) (
 	var sharedDirMounts []Mount
 	var ignoredMounts []Mount
 	for idx, m := range c.mounts {
-		if isSystemMount(m.Destination) || m.Type != "bind" {
+		if isSystemMount(m.Destination) {
+			if !(IsDockerVolume(m.Source) || Isk8sHostEmptyDir(m.Source)) {
+				continue
+			}
+		}
+
+		if m.Type != "bind" {
 			continue
 		}
 

virtcontainers/kata_agent.go

@@ -43,6 +43,15 @@ import (
 	grpcStatus "google.golang.org/grpc/status"
 )
 
+const (
+	// KataEphemeralDevType creates a tmpfs backed volume for sharing files between containers.
+	KataEphemeralDevType = "ephemeral"
+
+	// KataLocalDevType creates a local directory inside the VM for sharing files between
+	// containers.
+	KataLocalDevType = "local"
+)
+
 var (
 	checkRequestTimeout   = 30 * time.Second
 	defaultKataSocketName = "kata.sock"
@@ -59,17 +68,17 @@ var (
 	vsockSocketScheme     = "vsock"
 	// port numbers below 1024 are called privileged ports. Only a process with
 	// CAP_NET_BIND_SERVICE capability may bind to these port numbers.
-	vSockPort            = 1024
-	kata9pDevType        = "9p"
-	kataMmioBlkDevType   = "mmioblk"
-	kataBlkDevType       = "blk"
-	kataSCSIDevType      = "scsi"
-	kataNvdimmDevType    = "nvdimm"
-	sharedDir9pOptions   = []string{"trans=virtio,version=9p2000.L,cache=mmap", "nodev"}
-	shmDir               = "shm"
-	kataEphemeralDevType = "ephemeral"
-	ephemeralPath        = filepath.Join(kataGuestSandboxDir, kataEphemeralDevType)
-	grpcMaxDataSize      = int64(1024 * 1024)
+	vSockPort          = 1024
+	kata9pDevType      = "9p"
+	kataMmioBlkDevType = "mmioblk"
+	kataBlkDevType     = "blk"
+	kataSCSIDevType    = "scsi"
+	kataNvdimmDevType  = "nvdimm"
+	sharedDir9pOptions = []string{"trans=virtio,version=9p2000.L,cache=mmap", "nodev"}
+	shmDir             = "shm"
+	ephemeralPath      = filepath.Join(kataGuestSandboxDir, KataEphemeralDevType)
+	grpcMaxDataSize    = int64(1024 * 1024)
+	localDirOptions    = []string{"mode=0777"}
 )
 
 // KataAgentConfig is a structure storing information needed
@@ -672,7 +681,7 @@ func (k *kataAgent) startSandbox(sandbox *Sandbox) error {
 		shmSizeOption := fmt.Sprintf("size=%d", sandbox.shmSize)
 
 		shmStorage := &grpc.Storage{
-			Driver:     kataEphemeralDevType,
+			Driver:     KataEphemeralDevType,
 			MountPoint: path,
 			Source:     "shm",
 			Fstype:     "tmpfs",
@@ -1038,6 +1047,9 @@ func (k *kataAgent) createContainer(sandbox *Sandbox, c *Container) (p *Process,
 	epheStorages := k.handleEphemeralStorage(ociSpec.Mounts)
 	ctrStorages = append(ctrStorages, epheStorages...)
 
+	localStorages := k.handleLocalStorage(ociSpec.Mounts, sandbox.id)
+	ctrStorages = append(ctrStorages, localStorages...)
+
 	// We replace all OCI mount sources that match our container mount
 	// with the right source path (The guest one).
 	if err = k.replaceOCIMountSource(ociSpec, newMounts); err != nil {
@@ -1116,14 +1128,14 @@ func (k *kataAgent) createContainer(sandbox *Sandbox, c *Container) (p *Process,
 func (k *kataAgent) handleEphemeralStorage(mounts []specs.Mount) []*grpc.Storage {
 	var epheStorages []*grpc.Storage
 	for idx, mnt := range mounts {
-		if mnt.Type == kataEphemeralDevType {
+		if mnt.Type == KataEphemeralDevType {
 			// Set the mount source path to a path that resides inside the VM
 			mounts[idx].Source = filepath.Join(ephemeralPath, filepath.Base(mnt.Source))
 
 			// Create a storage struct so that kata agent is able to create
 			// tmpfs backed volume inside the VM
 			epheStorage := &grpc.Storage{
-				Driver:     kataEphemeralDevType,
+				Driver:     KataEphemeralDevType,
 				Source:     "tmpfs",
 				Fstype:     "tmpfs",
 				MountPoint: mounts[idx].Source,
@@ -1134,6 +1146,34 @@ func (k *kataAgent) handleEphemeralStorage(mounts []specs.Mount) []*grpc.Storage
 	return epheStorages
 }
 
+// handleLocalStorage handles local storage within the VM
+// by creating a directory in the VM from the source of the mount point.
+func (k *kataAgent) handleLocalStorage(mounts []specs.Mount, sandboxID string) []*grpc.Storage {
+	var localStorages []*grpc.Storage
+	for idx, mnt := range mounts {
+		if mnt.Type == KataLocalDevType {
+			// Set the mount source path to a the desired directory point in the VM.
+			// In this case it is located in the sandbox directory.
+			// We rely on the fact that the first container in the VM has the same ID as the sandbox ID.
+			// In Kubernetes, this is usually the pause container and we depend on it existing for
+			// local directories to work.
+			mounts[idx].Source = filepath.Join(kataGuestSharedDir, sandboxID, KataLocalDevType, filepath.Base(mnt.Source))
+
+			// Create a storage struct so that the kata agent is able to create the
+			// directory inside the VM.
+			localStorage := &grpc.Storage{
+				Driver:     KataLocalDevType,
+				Source:     KataLocalDevType,
+				Fstype:     KataLocalDevType,
+				MountPoint: mounts[idx].Source,
+				Options:    localDirOptions,
+			}
+			localStorages = append(localStorages, localStorage)
+		}
+	}
+	return localStorages
+}
+
 // handleBlockVolumes handles volumes that are block devices files
 // by passing the block devices as Storage to the agent.
 func (k *kataAgent) handleBlockVolumes(c *Container) []*grpc.Storage {

virtcontainers/kata_agent_test.go

@@ -365,7 +365,7 @@ func TestHandleEphemeralStorage(t *testing.T) {
 	mountSource := "/tmp/mountPoint"
 
 	mount := specs.Mount{
-		Type:   kataEphemeralDevType,
+		Type:   KataEphemeralDevType,
 		Source: mountSource,
 	}
 

virtcontainers/mount.go

@@ -326,3 +326,69 @@ func bindUnmountAllRootfs(ctx context.Context, sharedDir string, sandbox *Sandbo
 		}
 	}
 }
+
+const (
+	dockerVolumePrefix = "/var/lib/docker/volumes"
+	dockerVolumeSuffix = "_data"
+)
+
+// IsDockerVolume returns true if the given source path is
+// a docker volume.
+// This uses a very specific path that is used by docker.
+func IsDockerVolume(path string) bool {
+	if strings.HasPrefix(path, dockerVolumePrefix) && filepath.Base(path) == dockerVolumeSuffix {
+		return true
+	}
+	return false
+}
+
+const (
+	// K8sEmptyDir is the k8s specific path for `empty-dir` volumes
+	K8sEmptyDir = "kubernetes.io~empty-dir"
+)
+
+// IsEphemeralStorage returns true if the given path
+// to the storage belongs to kubernetes ephemeral storage
+//
+// This method depends on a specific path used by k8s
+// to detect if it's of type ephemeral. As of now,
+// this is a very k8s specific solution that works
+// but in future there should be a better way for this
+// method to determine if the path is for ephemeral
+// volume type
+func IsEphemeralStorage(path string) bool {
+	if !isEmptyDir(path) {
+		return false
+	}
+
+	if _, fsType, _ := GetDevicePathAndFsType(path); fsType == "tmpfs" {
+		return true
+	}
+
+	return false
+}
+
+// Isk8sHostEmptyDir returns true if the given path
+// to the storage belongs to kubernetes empty-dir of medium "default"
+// i.e volumes that are directories on the host.
+func Isk8sHostEmptyDir(path string) bool {
+	if !isEmptyDir(path) {
+		return false
+	}
+
+	if _, fsType, _ := GetDevicePathAndFsType(path); fsType != "tmpfs" {
+		return true
+	}
+	return false
+}
+
+func isEmptyDir(path string) bool {
+	splitSourceSlice := strings.Split(path, "/")
+	if len(splitSourceSlice) > 1 {
+		storageType := splitSourceSlice[len(splitSourceSlice)-2]
+		if storageType == K8sEmptyDir {
+			return true
+		}
+	}
+	return false
+}

virtcontainers/mount_test.go

@@ -9,6 +9,8 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"github.com/stretchr/testify/assert"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -18,6 +20,11 @@ import (
 	"testing"
 )
 
+const (
+	testDisabledNeedRoot = "Test disabled as requires root user"
+	testDirMode          = os.FileMode(0750)
+)
+
 func TestIsSystemMount(t *testing.T) {
 	tests := []struct {
 		mnt      string
@@ -282,3 +289,46 @@ func TestIsDeviceMapper(t *testing.T) {
 		t.Fatal()
 	}
 }
+
+func TestIsDockerVolume(t *testing.T) {
+	path := "/var/lib/docker/volumes/00da1347c7cf4f15db35f/_data"
+	isDockerVolume := IsDockerVolume(path)
+	assert.True(t, isDockerVolume)
+
+	path = "/var/lib/testdir"
+	isDockerVolume = IsDockerVolume(path)
+	assert.False(t, isDockerVolume)
+}
+
+func TestIsEphemeralStorage(t *testing.T) {
+	if os.Geteuid() != 0 {
+		t.Skip(testDisabledNeedRoot)
+	}
+
+	dir, err := ioutil.TempDir(testDir, "foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	sampleEphePath := filepath.Join(dir, K8sEmptyDir, "tmp-volume")
+	err = os.MkdirAll(sampleEphePath, testDirMode)
+	assert.Nil(t, err)
+
+	err = syscall.Mount("tmpfs", sampleEphePath, "tmpfs", 0, "")
+	assert.Nil(t, err)
+	defer syscall.Unmount(sampleEphePath, 0)
+
+	isEphe := IsEphemeralStorage(sampleEphePath)
+	assert.True(t, isEphe)
+
+	isHostEmptyDir := Isk8sHostEmptyDir(sampleEphePath)
+	assert.False(t, isHostEmptyDir)
+
+	sampleEphePath = "/var/lib/kubelet/pods/366c3a75-4869-11e8-b479-507b9ddd5ce4/volumes/cache-volume"
+	isEphe = IsEphemeralStorage(sampleEphePath)
+	assert.False(t, isEphe)
+
+	isHostEmptyDir = Isk8sHostEmptyDir(sampleEphePath)
+	assert.False(t, isHostEmptyDir)
+}