Short-term kludges for recent AdditionalLayerStore changes

storage/storage_dest.go

@@ -388,11 +388,17 @@ func (s *storageImageDestination) tryReusingBlobAsPending(blobDigest digest.Dige
 		if err != nil && !errors.Is(err, storage.ErrLayerUnknown) {
 			return false, private.ReusedBlob{}, fmt.Errorf(`looking for compressed layers with digest %q and labels: %w`, blobDigest, err)
 		} else if err == nil {
-			d := aLayer.TOCDigest()
-			if d == "" {
-				return false, private.ReusedBlob{}, fmt.Errorf(`failed to get TOCDigest of %q: %w`, blobDigest, err)
+			alsTOCDigest := aLayer.TOCDigest()
+			if alsTOCDigest != options.TOCDigest {
+				// FIXME: If alsTOCDigest is "", the Additional Layer Store FUSE server is probably just too old, and we could
+				// probably go on reading the layer from other sources.
+				//
+				// Currently it should not be possible for alsTOCDigest to be set and not the expected value, but there’s
+				// not that much benefit to checking for equality — we trust the FUSE server to validate the digest either way.
+				return false, private.ReusedBlob{}, fmt.Errorf("additional layer for TOCDigest %q reports unexpected TOCDigest %q",
+					options.TOCDigest, alsTOCDigest)
 			}
-			s.lockProtected.indexToTOCDigest[*options.LayerIndex] = d
+			s.lockProtected.indexToTOCDigest[*options.LayerIndex] = options.TOCDigest
 			s.lockProtected.indexToAdditionalLayer[*options.LayerIndex] = aLayer
 			return true, private.ReusedBlob{
 				Digest: blobDigest,

storage/storage_src.go

@@ -307,9 +307,6 @@ func (s *storageImageSource) LayerInfosForCopy(ctx context.Context, instanceDige
 		if err != nil {
 			return nil, fmt.Errorf("reading layer %q in image %q: %w", layerID, s.image.ID, err)
 		}
-		if layer.UncompressedSize < 0 {
-			layer.UncompressedSize = -1
-		}
 
 		blobDigest := layer.UncompressedDigest
 		if blobDigest == "" {
@@ -331,12 +328,16 @@ func (s *storageImageSource) LayerInfosForCopy(ctx context.Context, instanceDige
 				return nil, fmt.Errorf("parsing expected diffID %q for layer %q: %w", expectedDigest, layerID, err)
 			}
 		}
+		size := layer.UncompressedSize
+		if size < 0 {
+			size = -1
+		}
 		s.getBlobMutex.Lock()
 		s.getBlobMutexProtected.digestToLayerID[blobDigest] = layer.ID
 		s.getBlobMutex.Unlock()
 		blobInfo := types.BlobInfo{
 			Digest:    blobDigest,
-			Size:      layer.UncompressedSize,
+			Size:      size,
 			MediaType: uncompressedLayerType,
 		}
 		physicalBlobInfos = append([]types.BlobInfo{blobInfo}, physicalBlobInfos...)
@@ -455,10 +456,13 @@ func (s *storageImageSource) getSize() (int64, error) {
 		if (layer.TOCDigest == "" && layer.UncompressedDigest == "") || (layer.TOCDigest == "" && layer.UncompressedSize < 0) {
 			return -1, fmt.Errorf("size for layer %q is unknown, failing getSize()", layerID)
 		}
-		if layer.UncompressedSize < 0 {
-			sum = 0
+		// FIXME: We allow layer.UncompressedSize < 0 above, because currently images in an Additional Layer Store don’t provide that value.
+		// Right now, various callers in Podman (and, also, newImage in this package) don’t expect the size computation to fail.
+		// Should we update the callers, or do we need to continue returning inaccurate information here? Or should we pay the cost
+		// to compute the size from the diff?
+		if layer.UncompressedSize >= 0 {
+			sum += layer.UncompressedSize
 		}
-		sum += layer.UncompressedSize
 		if layer.Parent == "" {
 			break
 		}