Introduce new kubelet volume manager

This commit adds a new volume manager in kubelet that synchronizes
volume mount/unmount (and attach/detach, if attach/detach controller
is not enabled).

This eliminates the race conditions between the pod creation loop
and the orphaned volumes loops. It also removes the unmount/detach
from the `syncPod()` path so volume clean up never blocks the
`syncPod` loop.

pkg/volume/plugins.go

@@ -18,6 +18,7 @@ package volume
 
 import (
 	"fmt"
+	"net"
 	"strings"
 	"sync"
 
@@ -35,12 +36,6 @@ import (
 
 // VolumeOptions contains option information about a volume.
 type VolumeOptions struct {
-	// The rootcontext to use when performing mounts for a volume. This is a
-	// temporary measure in order to set the rootContext of tmpfs mounts
-	// correctly. it will be replaced and expanded on by future
-	// SecurityContext work.
-	RootContext string
-
 	// The attributes below are required by volume.Provisioner
 	// TODO: refactor all of this out of volumes when an admin can configure
 	// many kinds of provisioners.
@@ -86,6 +81,11 @@ type VolumePlugin interface {
 	// const.
 	CanSupport(spec *Spec) bool
 
+	// RequiresRemount returns true if this plugin requires mount calls to be
+	// reexecuted. Atomically updating volumes, like Downward API, depend on
+	// this to update the contents of the volume.
+	RequiresRemount() bool
+
 	// NewMounter creates a new volume.Mounter from an API specification.
 	// Ownership of the spec pointer in *not* transferred.
 	// - spec: The api.Volume spec
@@ -196,6 +196,15 @@ type VolumeHost interface {
 
 	// Returns the hostname of the host kubelet is running on
 	GetHostName() string
+
+	// Returns host IP or nil in the case of error.
+	GetHostIP() (net.IP, error)
+
+	// Returns the rootcontext to use when performing mounts for a volume.
+	// This is a temporary measure in order to set the rootContext of tmpfs
+	// mounts correctly. It will be replaced and expanded on by future
+	// SecurityContext work.
+	GetRootContext() string
 }
 
 // VolumePluginMgr tracks registered plugins.