devmapper: Properly restore mocked functions after test

Currently the tests that mocks or denies functions leave this state
around for the next test. This is no good if we want to actually
test the devicemapper code in later tests.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

daemon/graphdriver/devmapper/driver_test.go

@@ -20,8 +20,16 @@ func init() {
 	DefaultBaseFsSize = 300 * 1024 * 1024
 }
 
+// We use assignment here to get the right type
+var (
+	oldMounted = Mounted
+	oldExecRun = execRun
+)
+
 // denyAllDevmapper mocks all calls to libdevmapper in the unit tests, and denies them by default
 func denyAllDevmapper() {
+	oldExecRun = execRun
+
 	// Hijack all calls to libdevmapper with default panics.
 	// Authorized calls are selectively hijacked in each tests.
 	DmTaskCreate = func(t int) *CDmTask {
@@ -77,7 +85,29 @@ func denyAllDevmapper() {
 	}
 }
 
+func restoreAllDevmapper() {
+	DmGetLibraryVersion = dmGetLibraryVersionFct
+	DmGetNextTarget = dmGetNextTargetFct
+	DmLogInitVerbose = dmLogInitVerboseFct
+	DmSetDevDir = dmSetDevDirFct
+	DmTaskAddTarget = dmTaskAddTargetFct
+	DmTaskCreate = dmTaskCreateFct
+	DmTaskDestroy = dmTaskDestroyFct
+	DmTaskGetInfo = dmTaskGetInfoFct
+	DmTaskRun = dmTaskRunFct
+	DmTaskSetAddNode = dmTaskSetAddNodeFct
+	DmTaskSetCookie = dmTaskSetCookieFct
+	DmTaskSetMessage = dmTaskSetMessageFct
+	DmTaskSetName = dmTaskSetNameFct
+	DmTaskSetRo = dmTaskSetRoFct
+	DmTaskSetSector = dmTaskSetSectorFct
+	DmUdevWait = dmUdevWaitFct
+	LogWithErrnoInit = logWithErrnoInitFct
+	execRun = oldExecRun
+}
+
 func denyAllSyscall() {
+	oldMounted = Mounted
 	sysMount = func(source, target, fstype string, flags uintptr, data string) (err error) {
 		panic("sysMount: this method should not be called here")
 	}
@@ -110,6 +140,14 @@ func denyAllSyscall() {
 	// }
 }
 
+func restoreAllSyscall() {
+	sysMount = syscall.Mount
+	sysUnmount = syscall.Unmount
+	sysCloseOnExec = syscall.CloseOnExec
+	sysSyscall = syscall.Syscall
+	Mounted = oldMounted
+}
+
 func mkTestDirectory(t *testing.T) string {
 	dir, err := ioutil.TempDir("", "docker-test-devmapper-")
 	if err != nil {
@@ -160,8 +198,10 @@ func TestInit(t *testing.T) {
 	)
 	defer osRemoveAll(home)
 
+	denyAllDevmapper()
+	defer restoreAllDevmapper()
+
 	func() {
-		denyAllDevmapper()
 		DmSetDevDir = func(dir string) int {
 			calls["DmSetDevDir"] = true
 			expectedDir := "/dev"
@@ -398,7 +438,7 @@ func mockAllDevmapper(calls Set) {
 
 func TestDriverName(t *testing.T) {
 	denyAllDevmapper()
-	defer denyAllDevmapper()
+	defer restoreAllDevmapper()
 
 	oldInit := fakeInit()
 	defer restoreInit(oldInit)
@@ -412,8 +452,8 @@ func TestDriverName(t *testing.T) {
 func TestDriverCreate(t *testing.T) {
 	denyAllDevmapper()
 	denyAllSyscall()
-	defer denyAllSyscall()
-	defer denyAllDevmapper()
+	defer restoreAllSyscall()
+	defer restoreAllDevmapper()
 
 	calls := make(Set)
 	mockAllDevmapper(calls)
@@ -524,8 +564,8 @@ func TestDriverCreate(t *testing.T) {
 func TestDriverRemove(t *testing.T) {
 	denyAllDevmapper()
 	denyAllSyscall()
-	defer denyAllSyscall()
-	defer denyAllDevmapper()
+	defer restoreAllSyscall()
+	defer restoreAllDevmapper()
 
 	calls := make(Set)
 	mockAllDevmapper(calls)