image: propagate errors from extractRootfs

every error from copier.Get was previously lost and not propagated
back.  That caused the caller to believe the operation was successful
and lead to incomplete images on errors.

Signed-off-by: Giuseppe Scrivano <[email protected]>

image.go

@@ -146,14 +146,16 @@ func computeLayerMIMEType(what string, layerCompression archive.Compression) (om
 }
 
 // Extract the container's whole filesystem as if it were a single layer.
-func (i *containerImageRef) extractRootfs() (io.ReadCloser, error) {
+func (i *containerImageRef) extractRootfs() (io.ReadCloser, chan error, error) {
 	var uidMap, gidMap []idtools.IDMap
 	mountPoint, err := i.store.Mount(i.containerID, i.mountLabel)
 	if err != nil {
-		return nil, errors.Wrapf(err, "error mounting container %q", i.containerID)
+		return nil, nil, errors.Wrapf(err, "error mounting container %q", i.containerID)
 	}
 	pipeReader, pipeWriter := io.Pipe()
+	errChan := make(chan error, 1)
 	go func() {
+		defer close(errChan)
 		if i.idMappingOptions != nil {
 			uidMap, gidMap = convertRuntimeIDMaps(i.idMappingOptions.UIDMap, i.idMappingOptions.GIDMap)
 		}
@@ -162,7 +164,9 @@ func (i *containerImageRef) extractRootfs() (io.ReadCloser, error) {
 			GIDMap: gidMap,
 		}
 		err = copier.Get(mountPoint, mountPoint, copierOptions, []string{"."}, pipeWriter)
+		errChan <- err
 		pipeWriter.Close()
+
 	}()
 	return ioutils.NewReadCloserWrapper(pipeReader, func() error {
 		if err = pipeReader.Close(); err != nil {
@@ -175,7 +179,7 @@ func (i *containerImageRef) extractRootfs() (io.ReadCloser, error) {
 			err = err2
 		}
 		return err
-	}), nil
+	}), errChan, nil
 }
 
 // Build fresh copies of the container configuration structures so that we can edit them
@@ -357,9 +361,10 @@ func (i *containerImageRef) NewImageSource(ctx context.Context, sc *types.System
 			Compression: &noCompression,
 		}
 		var rc io.ReadCloser
+		var errChan chan error
 		if i.squash {
 			// Extract the root filesystem as a single layer.
-			rc, err = i.extractRootfs()
+			rc, errChan, err = i.extractRootfs()
 			if err != nil {
 				return nil, err
 			}
@@ -417,6 +422,14 @@ func (i *containerImageRef) NewImageSource(ctx context.Context, sc *types.System
 		writeCloser.Close()
 		layerFile.Close()
 		rc.Close()
+
+		if errChan != nil {
+			err = <-errChan
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		if err != nil {
 			return nil, errors.Wrapf(err, "error storing %s to file", what)
 		}