lib/backup: add MustStop() method for all remote filesystems

app/vmbackup/main.go

@@ -91,6 +91,8 @@ func main() {
 		logger.Fatalf("cannot create backup: %s", err)
 	}
 	srcFS.MustStop()
+	dstFS.MustStop()
+	originFS.MustStop()
 }
 
 func usage() {

app/vmrestore/main.go

@@ -52,6 +52,7 @@ func main() {
 	if err := a.Run(); err != nil {
 		logger.Fatalf("cannot restore from backup: %s", err)
 	}
+	srcFS.MustStop()
 	dstFS.MustStop()
 }
 

lib/backup/common/fs.go

@@ -9,6 +9,9 @@ import (
 // This filesystem is used for performing server-side file copies
 // instead of uploading data from local filesystem.
 type OriginFS interface {
+	// MustStop must be called when the RemoteFS is no longer needed.
+	MustStop()
+
 	// String must return human-readable representation of OriginFS.
 	String() string
 
@@ -18,6 +21,9 @@ type OriginFS interface {
 
 // RemoteFS is a filesystem where backups are stored.
 type RemoteFS interface {
+	// MustStop must be called when the RemoteFS is no longer needed.
+	MustStop()
+
 	// String must return human-readable representation of RemoteFS.
 	String() string
 

lib/backup/fsnil/fsnil.go

@@ -7,6 +7,11 @@ import (
 // FS represents nil remote filesystem.
 type FS struct{}
 
+// MustStop stops fs.
+func (fs *FS) MustStop() {
+	// Nothing to do
+}
+
 // String returns human-readable string representation for fs.
 func (fs *FS) String() string {
 	return "fsnil"

lib/backup/fsremote/fsremote.go

@@ -22,6 +22,11 @@ type FS struct {
 	Dir string
 }
 
+// MustStop stops fs.
+func (fs *FS) MustStop() {
+	// Nothing to do
+}
+
 // String returns human-readable string representation for fs.
 func (fs *FS) String() string {
 	return fmt.Sprintf("fsremote %q", fs.Dir)

lib/backup/gcsremote/gcs.go

@@ -33,6 +33,8 @@ type FS struct {
 }
 
 // Init initializes fs.
+//
+// The returned fs must be stopped when no long needed with MustStop call.
 func (fs *FS) Init() error {
 	if fs.bkt != nil {
 		logger.Panicf("BUG: fs.Init has been already called")
@@ -63,6 +65,11 @@ func (fs *FS) Init() error {
 	return nil
 }
 
+// MustStop stops fs.
+func (fs *FS) MustStop() {
+	fs.bkt = nil
+}
+
 // String returns human-readable description for fs.
 func (fs *FS) String() string {
 	return fmt.Sprintf("GCS{bucket: %q, dir: %q}", fs.Bucket, fs.Dir)

lib/backup/s3remote/s3.go

@@ -45,6 +45,8 @@ type FS struct {
 }
 
 // Init initializes fs.
+//
+// The returned fs must be stopped when no long needed with MustStop call.
 func (fs *FS) Init() error {
 	if fs.s3 != nil {
 		logger.Panicf("BUG: Init is already called")
@@ -96,6 +98,12 @@ func (fs *FS) Init() error {
 	return nil
 }
 
+// MustStop stops fs.
+func (fs *FS) MustStop() {
+	fs.s3 = nil
+	fs.uploader = nil
+}
+
 // String returns human-readable description for fs.
 func (fs *FS) String() string {
 	return fmt.Sprintf("S3{bucket: %q, dir: %q}", fs.Bucket, fs.Dir)