From 121e1f3ddc5764ddfb792c317bcd06219769d2d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Vl=C3=A9rick?= <pvlerick@gmail.com>
Date: Sat, 24 Jun 2023 15:27:05 +0200
Subject: [PATCH] Implementing the shared blob case logic
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Philippe Vlérick <pvlerick@gmail.com>
---
 oci/layout/oci_transport.go      | 39 ++++++++++++++++++++++++--------
 oci/layout/oci_transport_test.go |  2 +-
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/oci/layout/oci_transport.go b/oci/layout/oci_transport.go
index 653e35128c..1a7c791262 100644
--- a/oci/layout/oci_transport.go
+++ b/oci/layout/oci_transport.go
@@ -249,19 +249,43 @@ func (ref ociReference) NewImageDestination(ctx context.Context, sys *types.Syst
 func (ref ociReference) DeleteImage(ctx context.Context, sys *types.SystemContext) error {
 
 	// Get the manifest for the image
-	descriptor, err := ref.getManifestDescriptor()
+	manifestDescriptor, err := ref.getManifestDescriptor()
 	if err != nil {
 		return err
 	}
 
-	manifest, err := ref.getManifest(descriptor)
+	manifest, err := ref.getManifest(manifestDescriptor)
 	if err != nil {
 		return err
 	}
 
+	// Get all the layers used by all other images
+	index, err := ref.getIndex()
+	if err != nil {
+		return err
+	}
+	layersUsedByOtherImages := make(map[digest.Digest]bool, len(index.Manifests))
+	for _, v := range index.Manifests {
+		if v.Digest != manifestDescriptor.Digest {
+			otherImageManifest, err := ref.getManifest(v)
+			if err != nil {
+				return err
+			}
+			for _, layer := range otherImageManifest.Layers {
+				layersUsedByOtherImages[layer.Digest] = true
+			}
+		}
+	}
+
 	// Delete all blobs
-	for _, d := range append(manifest.Layers, manifest.Config, descriptor) {
-		blobPath, err := ref.blobPath(d.Digest, "")
+	blobsToDelete := make([]digest.Digest, 0, len(manifest.Layers))
+	for _, layer := range manifest.Layers {
+		if !layersUsedByOtherImages[layer.Digest] {
+			blobsToDelete = append(blobsToDelete, layer.Digest)
+		}
+	}
+	for _, digest := range append(blobsToDelete, manifest.Config.Digest, manifestDescriptor.Digest) {
+		blobPath, err := ref.blobPath(digest, "")
 		if err != nil {
 			return err
 		}
@@ -272,14 +296,9 @@ func (ref ociReference) DeleteImage(ctx context.Context, sys *types.SystemContex
 	}
 
 	// Update the index
-	index, err := ref.getIndex()
-	if err != nil {
-		return err
-	}
-
 	newManifests := make([]imgspecv1.Descriptor, 0, len(index.Manifests)-1)
 	for _, v := range index.Manifests {
-		if v.Digest != descriptor.Digest {
+		if v.Digest != manifestDescriptor.Digest {
 			newManifests = append(newManifests, v)
 		}
 	}
diff --git a/oci/layout/oci_transport_test.go b/oci/layout/oci_transport_test.go
index c3587c7d8a..eb699dd8fa 100644
--- a/oci/layout/oci_transport_test.go
+++ b/oci/layout/oci_transport_test.go
@@ -576,7 +576,7 @@ func TestReferenceDeleteImage_someLayersAreReferencedByOtherImages(t *testing.T)
 	blobDoesNotExist(t, blobsDir, image.layers[0])
 	blobDoesNotExist(t, blobsDir, image.layers[2])
 
-	// Check that the blob used by another image is still there
+	// Check that the blob used by another image was not deleted
 	commonBlobDigest, err := digest.Parse(commonLayer)
 	require.NoError(t, err)
 	_, err = os.Stat(filepath.Join(blobsDir, commonBlobDigest.Algorithm().String(), commonBlobDigest.Hex()))