Don't re-run migration if aufs and overlay roots exist

Signed-off-by: Robert Günzler <robertg@balena.io>

daemon/daemon.go

@@ -942,21 +942,26 @@ func NewDaemon(ctx context.Context, config *config.Config, pluginStore *plugin.S
 		start := time.Now()
 		var err error
 		err = storagemigration.Migrate(config.Root)
-		// gracefully handle non-existing aufs root
-		// we have nothing to migrate from
-		if err != nil && err != storagemigration.ErrAuFSRootNotExists {
-			if err := storagemigration.FailCleanup(config.Root); err != nil {
-				return nil, errors.Wrap(err, "failed to cleanup after failed migration")
+		if err != nil {
+			if err == storagemigration.ErrAuFSRootNotExists ||
+				err == storagemigration.ErrOverlayRootExists {
+				// gracefully handle missing aufs root or existing
+				// overlay root - we have nothing to migrate from
+				logrus.Infof("Storage migartion skipped: %s", err)
+			} else {
+				// rollback on errors
+				if err := storagemigration.FailCleanup(config.Root); err != nil {
+					return nil, errors.Wrap(err, "failed to cleanup after failed storage migration")
+				}
+				return nil, errors.Wrap(err, "failed to migrate storage")
 			}
-			return nil, errors.Wrap(err, "failed to migrate storage")
-		}
-		// only commit if migration succeded
-		if err == nil {
+		} else {
+			// only commit if migration succeded
 			if err := storagemigration.Commit(config.Root); err != nil {
 				return nil, errors.Wrap(err, "failed to commit storage migration")
 			}
+			logrus.Infof("Storage migration from aufs to overlay2, took %s", time.Now().Sub(start))
 		}
-		logrus.Infof("Storage migration from aufs to overlay2, took %s", time.Now().Sub(start))
 	}
 
 	for operatingSystem, gd := range d.graphDrivers {

pkg/storagemigration/migrate.go

@@ -22,15 +22,10 @@ func Migrate(root string) error {
 		return err
 	}
 
-	// TODO this needs to go... we can't overwrite the previous migration
 	// make sure there isn't an overlay2 tree already
 	err = CheckOvlRootExists(root)
 	if err == nil {
-		logrus.Warn("overlay root found, cleaning up...")
-		err := os.RemoveAll(overlayRoot(root))
-		if err != nil {
-			return fmt.Errorf("Error cleaning up overlay2 root: %v", err)
-		}
+		return ErrOverlayRootExists
 	}
 
 	var state State

pkg/storagemigration/overlayutils.go

@@ -16,6 +16,8 @@ import (
 var (
 	// ErrOverlayRootNotExists indicates the overlay2 root directory wasn't found
 	ErrOverlayRootNotExists = errors.New("Overlay2 root doesn't exists")
+	// ErrOverlayRootExists indicates the migration was already run sucessfully
+	ErrOverlayRootExists = errors.New("Overlay2 root exists")
 )
 
 // CheckRootExists checks for the overlay storage root directory

pkg/storagemigration/storagemigration.go

@@ -1,4 +1,3 @@
-// TODO we can probably re-use containerd libs?
 package storagemigration
 
 import "path/filepath"
@@ -29,9 +28,6 @@ const (
 	MetaWhiteout
 
 	// MetaOther is a catch-all for everything else
-	//
-	// TODO(robertgzr): replace this with more meta types
-	// for better mapping from a->o, o->a
 	MetaOther
 )