Add TmpfsRoot option

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

factory_linux.go

@@ -10,7 +10,9 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"syscall"
 
+	"github.com/docker/docker/pkg/mount"
 	"github.com/docker/libcontainer/cgroups"
 	"github.com/docker/libcontainer/cgroups/fs"
 	"github.com/docker/libcontainer/cgroups/systemd"
@@ -78,6 +80,20 @@ func Cgroupfs(l *LinuxFactory) error {
 	return nil
 }
 
+// TmpfsRoot is an option func to mount LinuxFactory.Root to tmpfs.
+func TmpfsRoot(l *LinuxFactory) error {
+	mounted, err := mount.Mounted(l.Root)
+	if err != nil {
+		return err
+	}
+	if !mounted {
+		if err := syscall.Mount("tmpfs", l.Root, "tmpfs", 0, ""); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // New returns a linux based container factory based in the root directory and
 // configures the factory with the provided option funcs.
 func New(root string, options ...func(*LinuxFactory) error) (Factory, error) {

factory_linux_test.go

@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/docker/docker/pkg/mount"
 	"github.com/docker/libcontainer/configs"
 )
 
@@ -17,9 +18,6 @@ func newTestRoot() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	if err := os.MkdirAll(dir, 0700); err != nil {
-		return "", err
-	}
 	return dir, nil
 }
 
@@ -49,6 +47,58 @@ func TestFactoryNew(t *testing.T) {
 	}
 }
 
+func TestFactoryNewTmpfs(t *testing.T) {
+	root, rerr := newTestRoot()
+	if rerr != nil {
+		t.Fatal(rerr)
+	}
+	defer os.RemoveAll(root)
+	factory, err := New(root, Cgroupfs, TmpfsRoot)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if factory == nil {
+		t.Fatal("factory should not be nil")
+	}
+	lfactory, ok := factory.(*LinuxFactory)
+	if !ok {
+		t.Fatal("expected linux factory returned on linux based systems")
+	}
+	if lfactory.Root != root {
+		t.Fatalf("expected factory root to be %q but received %q", root, lfactory.Root)
+	}
+
+	if factory.Type() != "libcontainer" {
+		t.Fatalf("unexpected factory type: %q, expected %q", factory.Type(), "libcontainer")
+	}
+	mounted, err := mount.Mounted(lfactory.Root)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !mounted {
+		t.Fatalf("Factory Root is not mounted")
+	}
+	mounts, err := mount.GetMounts()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found bool
+	for _, m := range mounts {
+		if m.Mountpoint == lfactory.Root {
+			if m.Fstype != "tmpfs" {
+				t.Fatalf("Fstype of root: %s, expected %s", m.Fstype, "tmpfs")
+			}
+			if m.Source != "tmpfs" {
+				t.Fatalf("Source of root: %s, expected %s", m.Source, "tmpfs")
+			}
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("Factory Root is not listed in mounts list")
+	}
+}
+
 func TestFactoryLoadNotExists(t *testing.T) {
 	root, rerr := newTestRoot()
 	if rerr != nil {

rootfs_linux.go

@@ -24,7 +24,7 @@ func setupRootfs(config *configs.Config, console *linuxConsole) (err error) {
 		return newSystemError(err)
 	}
 	for _, m := range config.Mounts {
-		if err := mount(m, config.Rootfs, config.MountLabel); err != nil {
+		if err := mountToRootfs(m, config.Rootfs, config.MountLabel); err != nil {
 			return newSystemError(err)
 		}
 	}
@@ -62,7 +62,7 @@ func setupRootfs(config *configs.Config, console *linuxConsole) (err error) {
 	return nil
 }
 
-func mount(m *configs.Mount, rootfs, mountLabel string) error {
+func mountToRootfs(m *configs.Mount, rootfs, mountLabel string) error {
 	var (
 		dest = m.Destination
 		data = label.FormatMountLabel(m.Data, mountLabel)