pkg/payload/precondition/clusterversion: Compare target metadata.previous, not rollback SemVer

pkg/cvo/cvo.go

@@ -938,7 +938,7 @@ func hasReachedLevel(cv *configv1.ClusterVersion, desired configv1.Update) bool
 
 func (optr *Operator) defaultPreconditionChecks() precondition.List {
 	return []precondition.Precondition{
-		preconditioncv.NewRollback(optr.currentVersion),
+		preconditioncv.NewMetadataUpdate(optr.currentVersion),
 		preconditioncv.NewUpgradeable(optr.cvLister),
 		preconditioncv.NewRecentEtcdBackup(optr.cvLister, optr.coLister),
 		preconditioncv.NewRecommendedUpdate(optr.cvLister),

pkg/cvo/sync_worker.go

@@ -371,6 +371,7 @@ func (w *SyncWorker) syncPayload(ctx context.Context, work *SyncWork,
 		} else {
 			if block, err := precondition.Summarize(w.preconditions.RunAll(ctx, precondition.ReleaseContext{
 				DesiredVersion: payloadUpdate.Release.Version,
+				Previous: payloadUpdate.Previous,
 			}), work.Desired.Force); err != nil {
 				klog.V(2).Infof("Precondition error (force %t, block %t): %v", work.Desired.Force, block, err)
 				if block {

pkg/payload/payload.go

@@ -114,6 +114,9 @@ type Update struct {
 
 	Architecture string
 
+	// Previous is a slice of valid previous versions.
+	Previous []string
+
 	// manifestHash is a hash of the manifests included in this payload
 	ManifestHash string
 	Manifests    []manifest.Manifest
@@ -313,7 +316,7 @@ func loadUpdatePayloadMetadata(dir, releaseImage, clusterProfile string) (*Updat
 		releaseDir = filepath.Join(dir, ReleaseManifestDir)
 	)
 
-	release, arch, err := loadReleaseFromMetadata(releaseDir)
+	release, arch, previous, err := loadReleaseFromMetadata(releaseDir)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -334,6 +337,7 @@ func loadUpdatePayloadMetadata(dir, releaseImage, clusterProfile string) (*Updat
 		Release:      release,
 		ImageRef:     imageRef,
 		Architecture: arch,
+		Previous:     previous,
 	}, tasks, nil
 }
 
@@ -357,7 +361,7 @@ func getPayloadTasks(releaseDir, cvoDir, releaseImage, clusterProfile string) []
 	}}
 }
 
-func loadReleaseFromMetadata(releaseDir string) (configv1.Release, string, error) {
+func loadReleaseFromMetadata(releaseDir string) (configv1.Release, string, []string, error) {
 	var release configv1.Release
 	path := filepath.Join(releaseDir, cincinnatiJSONFile)
 	data, err := os.ReadFile(path)
@@ -418,7 +422,9 @@ func loadReleaseFromMetadata(releaseDir string) (configv1.Release, string, error
 		}
 	}
 
-	return release, arch, nil
+	// FIXME: load Metadata["previous"]
+
+	return release, arch, previous, nil
 }
 
 func loadImageReferences(releaseDir string) (*imagev1.ImageStream, error) {

pkg/payload/precondition/clusterversion/metadata_update.go

@@ -0,0 +1,50 @@
+package clusterversion
+
+import (
+	"context"
+	"fmt"
+
+	configv1 "github.com/openshift/api/config/v1"
+
+	precondition "github.com/openshift/cluster-version-operator/pkg/payload/precondition"
+)
+
+// currentRelease is a callback for returning the version that is currently being reconciled.
+type currentRelease func() configv1.Release
+
+// MetadataUpdate blocks metadataUpdates from the version that is currently being reconciled.
+type MetadataUpdate struct {
+	currentRelease
+}
+
+// NewMetadataUpdate returns a new MetadataUpdate precondition check.
+func NewMetadataUpdate(fn currentRelease) *MetadataUpdate {
+	return &MetadataUpdate{
+		currentRelease: fn,
+	}
+}
+
+// Name returns Name for the precondition.
+func (pf *MetadataUpdate) Name() string { return "ClusterVersionMetadataUpdate" }
+
+// Run runs the MetadataUpdate precondition, blocking metadataUpdates from the
+// version that is currently being reconciled.  It returns a
+// PreconditionError when possible.
+func (p *MetadataUpdate) Run(ctx context.Context, releaseContext precondition.ReleaseContext) error {
+	currentRelease := p.currentRelease()
+	if releaseContext.DesiredVersion == currentRelease {
+		return nil
+	}
+
+	for _, previous in := range releaseContext.Previous {
+		if currentRelease == previous {
+			return nil
+		}
+	}
+
+	return &precondition.Error{
+		Reason:  "InvalidDesiredVersion",
+		Message: fmt.Sprintf("The current version %q is neither the desired version %q nor a version declared in the desired version's previous-release update metadata: %v", currentVersion, releaseContext.DesiredVersion, releaseContext.Previous)
+		Name:    p.Name(),
+	}
+}

pkg/payload/precondition/precondition.go

@@ -37,6 +37,9 @@ type ReleaseContext struct {
 	// where the author decided to use a different naming scheme, or
 	// to leave the version completely unset.
 	DesiredVersion string
+
+        // Previous is a slice of valid previous versions.
+        Previous []string
 }
 
 // Precondition defines the precondition check for a payload.