remove layer's link file by gc

The garbage-collect should remove unsed layer link file

P.S. This was originally contributed by @m-masataka, now I would like to take over it.
Thanks @m-masataka efforts with PR https://github.com/distribution/distribution/pull/2288

Signed-off-by: Liang Zheng <zhengliang0901@gmail.com>

registry/storage/garbagecollect.go

@@ -2,6 +2,7 @@ package storage
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"github.com/distribution/distribution/v3"
@@ -36,6 +37,7 @@ func MarkAndSweep(ctx context.Context, storageDriver driver.StorageDriver, regis
 
 	// mark
 	markSet := make(map[digest.Digest]struct{})
+	deleteLayerSet := make(map[string][]digest.Digest)
 	manifestArr := make([]ManifestDel, 0)
 	err := repositoryEnumerator.Enumerate(ctx, func(repoName string) error {
 		emit(repoName)
@@ -97,15 +99,32 @@ func MarkAndSweep(ctx context.Context, storageDriver driver.StorageDriver, regis
 			})
 		})
 
-		// In certain situations such as unfinished uploads, deleting all
+		if err != nil {
-		// tags in S3 or removing the _manifests folder manually, this
+			// In certain situations such as unfinished uploads, deleting all
-		// error may be of type PathNotFound.
+			// tags in S3 or removing the _manifests folder manually, this
-		//
+			// error may be of type PathNotFound.
-		// In these cases we can continue marking other manifests safely.
+			//
-		if _, ok := err.(driver.PathNotFoundError); ok {
+			// In these cases we can continue marking other manifests safely.
-			return nil
+			if _, ok := err.(driver.PathNotFoundError); !ok {
+				return err
+			}
+		}
+		blobService := repository.Blobs(ctx)
+		layerEnumerator, ok := blobService.(distribution.ManifestEnumerator)
+		if !ok {
+			return errors.New("unable to convert BlobService into ManifestEnumerator")
 		}
 
+		var deleteLayers []digest.Digest
+		err = layerEnumerator.Enumerate(ctx, func(dgst digest.Digest) error {
+			if _, ok := markSet[dgst]; !ok {
+				deleteLayers = append(deleteLayers, dgst)
+			}
+			return nil
+		})
+		if len(deleteLayers) > 0 {
+			deleteLayerSet[repoName] = deleteLayers
+		}
 		return err
 	})
 	if err != nil {
@@ -148,6 +167,15 @@ func MarkAndSweep(ctx context.Context, storageDriver driver.StorageDriver, regis
 		}
 	}
 
+	for repo, dgsts := range deleteLayerSet {
+		for _, dgst := range dgsts {
+			err = vacuum.RemoveLayer(repo, dgst)
+			if err != nil {
+				return fmt.Errorf("failed to delete layer link %s of repo %s: %v", dgst, repo, err)
+			}
+		}
+	}
+
 	return err
 }
 

registry/storage/garbagecollect_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/distribution/distribution/v3/internal/dcontext"
 	"github.com/distribution/distribution/v3/manifest/ocischema"
 	"github.com/distribution/distribution/v3/registry/storage/driver"
+	storagedriver "github.com/distribution/distribution/v3/registry/storage/driver"
 	"github.com/distribution/distribution/v3/registry/storage/driver/inmemory"
 	"github.com/distribution/distribution/v3/testutil"
 	"github.com/distribution/reference"
@@ -416,6 +417,47 @@ func TestDeleteManifestIndexIfTagNotFound(t *testing.T) {
 	}
 }
 
+func TestGCWithUnusedLayerLinkPath(t *testing.T) {
+	ctx := dcontext.Background()
+	d := inmemory.New()
+
+	registry := createRegistry(t, d)
+	repo := makeRepository(t, registry, "unusedlayerlink")
+	image := uploadRandomSchema2Image(t, repo)
+
+	for dgst := range image.layers {
+		layerLinkPath, err := pathFor(layerLinkPathSpec{name: "unusedlayerlink", digest: dgst})
+		if err != nil {
+			t.Fatal(err)
+		}
+		fileInfo, err := d.Stat(ctx, layerLinkPath)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if fileInfo == nil {
+			t.Fatalf("layer link path %s not found", layerLinkPath)
+		}
+	}
+
+	err := MarkAndSweep(dcontext.Background(), d, registry, GCOpts{
+		DryRun:         false,
+		RemoveUntagged: true,
+	})
+	if err != nil {
+		t.Fatalf("got error: %v, expected nil", err)
+	}
+	for dgst := range image.layers {
+		layerLinkPath, err := pathFor(layerLinkPathSpec{name: "unusedlayerlink", digest: dgst})
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = d.Stat(ctx, layerLinkPath)
+		if _, ok := err.(storagedriver.PathNotFoundError); !ok {
+			t.Fatalf("layer link path %s should be not found", layerLinkPath)
+		}
+	}
+}
+
 func TestGCWithUnknownRepository(t *testing.T) {
 	ctx := dcontext.Background()
 	d := inmemory.New()

registry/storage/vacuum.go

@@ -100,3 +100,18 @@ func (v Vacuum) RemoveRepository(repoName string) error {
 
 	return nil
 }
+
+// RemoveLayer removes a layer link path from the storage
+func (v Vacuum) RemoveLayer(repoName string, dgst digest.Digest) error {
+	layerLinkPath, err := pathFor(layerLinkPathSpec{name: repoName, digest: dgst})
+	if err != nil {
+		return err
+	}
+	dcontext.GetLogger(v.ctx).Infof("Deleting layer link path: %s", layerLinkPath)
+	err = v.driver.Delete(v.ctx, layerLinkPath)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}