mount: Add check for k8s host empty directory

k8s host empty-dir is equivalent to docker volumes.
For this case, we should just use the host directory even
for system directories.

Move the isEphemeral function to virtcontainers to not
introduce cyclic dependency.

Fixes #1417

Signed-off-by: Archana Shinde <archana.m.shinde@intel.com>

pkg/katautils/create.go

@@ -161,7 +161,7 @@ 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) {
+		if vc.IsEphemeralStorage(mnt.Source) {
 			ociSpec.Mounts[idx].Type = "ephemeral"
 		}
 	}

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) {

virtcontainers/container.go

@@ -477,8 +477,10 @@ func (c *Container) mountSharedDirMounts(hostSharedDir, guestSharedDir string) (
 	var sharedDirMounts []Mount
 	var ignoredMounts []Mount
 	for idx, m := range c.mounts {
-		if isSystemMount(m.Destination) && !IsDockerVolume(m.Source) {
-			continue
+		if isSystemMount(m.Destination) {
+			if !(IsDockerVolume(m.Source) || Isk8sHostEmptyDir(m.Source)) {
+				continue
+			}
 		}
 
 		if m.Type != "bind" {

virtcontainers/mount.go

@@ -342,3 +342,49 @@ func IsDockerVolume(path string) bool {
 	return false
 }
 
+const (
+	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
+}
+
+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
@@ -289,6 +296,39 @@ func TestIsDockerVolume(t *testing.T) {
 	assert.True(t, isDockerVolume)
 
 	path = "/var/lib/testdir"
-	isDockerVolume := IsDockerVolume(path)
+	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)
+}