Function applyDiffLayer

pkg/imgutil/commit/commit.go:533–565

applyDiffLayer will apply diff layer content created by createDiff into the snapshotter.

(ctx context.Context, name string, baseImg ocispec.Image, sn snapshots.Snapshotter, differ diff.Applier, diffDesc ocispec.Descriptor)

// applyDiffLayer will apply diff layer content created by createDiff into the snapshotter.
func applyDiffLayer(ctx context.Context, name string, baseImg ocispec.Image, sn snapshots.Snapshotter, differ diff.Applier, diffDesc ocispec.Descriptor) (retErr error) {
	var (
		key    = uniquePart() + "-" + name
		parent = identity.ChainID(baseImg.RootFS.DiffIDs).String()
	)

	mount, err := sn.Prepare(ctx, key, parent)
	if err != nil {
		return err
	}

	defer func() {
		if retErr != nil {
			// NOTE: the snapshotter should be hold by lease. Even
			// if the cleanup fails, the containerd gc can delete it.
			if err := sn.Remove(ctx, key); err != nil {
				log.G(ctx).Warnf("failed to cleanup aborted apply %s: %s", key, err)
			}
		}
	}()

	if _, err = differ.Apply(ctx, diffDesc, mount); err != nil {
		return err
	}

	if err = sn.Commit(ctx, name, key); err != nil {
		if errdefs.IsAlreadyExists(err) {
			return nil
		}
		return err
	}
	return nil
}

// copied from github.com/containerd/containerd/rootfs/apply.go
func uniquePart() string {