[Kubelet] Do not use custom mounter script for bind mounts, ext* and tmpfs mounts

pkg/util/mount/BUILD

@@ -22,6 +22,7 @@ go_library(
     tags = ["automanaged"],
     deps = [
         "//pkg/util/exec:go_default_library",
+        "//pkg/util/sets:go_default_library",
         "//vendor:github.com/golang/glog",
     ],
 )

pkg/util/mount/mount.go

@@ -30,7 +30,7 @@ import (
 
 const (
 	// Default mount command if mounter path is not specified
-	mount = "mount"
+	defaultMountCommand = "mount"
 )
 
 type Interface interface {
@@ -105,7 +105,7 @@ func New() Interface {
 func NewCustomMounter(mounterPath, mounterRootfsPath string) Interface {
 	// If mounter-path flag is not set, use default mount path
 	if mounterPath == "" {
-		mounterPath = mount
+		mounterPath = defaultMountCommand
 	}
 	if mounterRootfsPath == "" {
 		mounterRootfsPath = "/"

pkg/util/mount/mount_linux.go

@@ -25,13 +25,13 @@ import (
 	"io"
 	"os"
 	"os/exec"
-	"path"
 	"strconv"
 	"strings"
 	"syscall"
 
 	"github.com/golang/glog"
 	utilExec "k8s.io/kubernetes/pkg/util/exec"
+	"k8s.io/kubernetes/pkg/util/sets"
 )
 
 const (
@@ -63,18 +63,24 @@ type Mounter struct {
 // type, where kernel handles fs type for you. The mount 'options' is a list of options,
 // currently come from mount(8), e.g. "ro", "remount", "bind", etc. If no more option is
 // required, call Mount with an empty string list or nil.
-// Update source path to include a root filesystem override to make a containerized mounter (specified via `mounterPath`) work.
 func (mounter *Mounter) Mount(source string, target string, fstype string, options []string) error {
+	// Path to mounter binary. Set to mount accessible via $PATH by default.
+	// All Linux distros are expected to be shipped with a mount utility that an support bind mounts.
+	mounterPath := defaultMountCommand
 	bind, bindRemountOpts := isBind(options)
 	if bind {
-		err := doMount(mounter.mounterPath, path.Join(mounter.mounterRootfsPath, source), path.Join(mounter.mounterRootfsPath, target), fstype, []string{"bind"})
+		err := doMount(mounterPath, source, target, fstype, []string{"bind"})
 		if err != nil {
 			return err
 		}
-		return doMount(mounter.mounterPath, path.Join(mounter.mounterRootfsPath, source), path.Join(mounter.mounterRootfsPath, target), fstype, bindRemountOpts)
-	} else {
-		return doMount(mounter.mounterPath, source, path.Join(mounter.mounterRootfsPath, target), fstype, options)
+		return doMount(mounterPath, source, target, fstype, bindRemountOpts)
 	}
+	// These filesystem types are expected to be supported by the mount utility on the host across all Linux distros.
+	var defaultMounterFsTypes = sets.NewString("tmpfs", "ext4", "ext3", "ext2")
+	if !defaultMounterFsTypes.Has(fstype) {
+		mounterPath = mounter.mounterPath
+	}
+	return doMount(mounterPath, source, target, fstype, options)
 }
 
 // isBind detects whether a bind mount is being requested and makes the remount options to