fix: support simultaneous create diff for same parent snapshot

Signed-off-by: Qian Zhang <cosmoer@qq.com>
(cherry picked from commit 344431c)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

rootfs/diff.go

@@ -44,7 +44,7 @@ func CreateDiff(ctx context.Context, snapshotID string, sn snapshots.Snapshotter
 		return ocispec.Descriptor{}, err
 	}
 
-	lowerKey := fmt.Sprintf("%s-parent-view", info.Parent)
+	lowerKey := fmt.Sprintf("%s-parent-view-%s", info.Parent, uniquePart())
 	lower, err := sn.View(ctx, lowerKey, info.Parent)
 	if err != nil {
 		return ocispec.Descriptor{}, err
@@ -58,7 +58,7 @@ func CreateDiff(ctx context.Context, snapshotID string, sn snapshots.Snapshotter
 			return ocispec.Descriptor{}, err
 		}
 	} else {
-		upperKey := fmt.Sprintf("%s-view", snapshotID)
+		upperKey := fmt.Sprintf("%s-view-%s", snapshotID, uniquePart())
 		upper, err = sn.View(ctx, upperKey, snapshotID)
 		if err != nil {
 			return ocispec.Descriptor{}, err