diff --git a/distribution/xfer/download.go b/distribution/xfer/download.go
index 8ccccbcbfb..af1a3995d2 100644
--- a/distribution/xfer/download.go
+++ b/distribution/xfer/download.go
@@ -166,7 +166,7 @@ func (ldm *LayerDownloadManager) Download(ctx context.Context, initialRootFS ima
 		// Layer is not known to exist - download and register it.
 		progress.Update(progressOutput, descriptor.ID(), "Pulling fs layer")
 
-		var xferFunc DoFunc
+		var xferFunc doFunc
 		if topDownload != nil {
 			xferFunc = ldm.makeDownloadFunc(descriptor, "", topDownload)
 			defer topDownload.transfer.release(watcher)
@@ -228,7 +228,7 @@ func (ldm *LayerDownloadManager) Download(ctx context.Context, initialRootFS ima
 // complete before the registration step, and registers the downloaded data
 // on top of parentDownload's resulting layer. Otherwise, it registers the
 // layer on top of the ChainID given by parentLayer.
-func (ldm *LayerDownloadManager) makeDownloadFunc(descriptor DownloadDescriptor, parentLayer layer.ChainID, parentDownload *downloadTransfer) DoFunc {
+func (ldm *LayerDownloadManager) makeDownloadFunc(descriptor DownloadDescriptor, parentLayer layer.ChainID, parentDownload *downloadTransfer) doFunc {
 	return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer {
 		d := &downloadTransfer{
 			transfer:   newTransfer(),
@@ -392,7 +392,7 @@ func (ldm *LayerDownloadManager) makeDownloadFunc(descriptor DownloadDescriptor,
 // parentDownload. This function does not log progress output because it would
 // interfere with the progress reporting for sourceDownload, which has the same
 // Key.
-func (ldm *LayerDownloadManager) makeDownloadFuncFromDownload(descriptor DownloadDescriptor, sourceDownload *downloadTransfer, parentDownload *downloadTransfer) DoFunc {
+func (ldm *LayerDownloadManager) makeDownloadFuncFromDownload(descriptor DownloadDescriptor, sourceDownload *downloadTransfer, parentDownload *downloadTransfer) doFunc {
 	return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer {
 		d := &downloadTransfer{
 			transfer:   newTransfer(),
diff --git a/distribution/xfer/transfer.go b/distribution/xfer/transfer.go
index 1693708778..d5f96c8aea 100644
--- a/distribution/xfer/transfer.go
+++ b/distribution/xfer/transfer.go
@@ -263,13 +263,13 @@ func (t *xfer) close() {
 	t.mu.Unlock()
 }
 
-// DoFunc is a function called by the transferManager to actually perform
+// doFunc is a function called by the transferManager to actually perform
 // a transfer. It should be non-blocking. It should wait until the start channel
 // is closed before transferring any data. If the function closes inactive, that
 // signals to the transferManager that the job is no longer actively moving
 // data - for example, it may be waiting for a dependent transfer to finish.
 // This prevents it from taking up a slot.
-type DoFunc func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer
+type doFunc func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer
 
 // transferManager is used by LayerDownloadManager and LayerUploadManager to
 // schedule and deduplicate transfers. It is up to the transferManager
@@ -301,7 +301,7 @@ func (tm *transferManager) setConcurrency(concurrency int) {
 // transfer checks if a transfer matching the given key is in progress. If not,
 // it starts one by calling xferFunc. The caller supplies a channel which
 // receives progress output from the transfer.
-func (tm *transferManager) transfer(key string, xferFunc DoFunc, progressOutput progress.Output) (transfer, *watcher) {
+func (tm *transferManager) transfer(key string, xferFunc doFunc, progressOutput progress.Output) (transfer, *watcher) {
 	tm.mu.Lock()
 	defer tm.mu.Unlock()
 
diff --git a/distribution/xfer/transfer_test.go b/distribution/xfer/transfer_test.go
index 9faecb8766..305bb91662 100644
--- a/distribution/xfer/transfer_test.go
+++ b/distribution/xfer/transfer_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestTransfer(t *testing.T) {
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, start <-chan struct{}, _ chan<- struct{}) transfer {
 			select {
 			case <-start:
@@ -71,7 +71,7 @@ func TestConcurrencyLimit(t *testing.T) {
 	const concurrencyLimit = 3
 	var runningJobs int32
 
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, start <-chan struct{}, _ chan<- struct{}) transfer {
 			xfer := newTransfer()
 			go func() {
@@ -130,7 +130,7 @@ func TestInactiveJobs(t *testing.T) {
 	var runningJobs int32
 	testDone := make(chan struct{})
 
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer {
 			xfer := newTransfer()
 			go func() {
@@ -190,7 +190,7 @@ func TestInactiveJobs(t *testing.T) {
 func TestWatchRelease(t *testing.T) {
 	ready := make(chan struct{})
 
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, start <-chan struct{}, _ chan<- struct{}) transfer {
 			xfer := newTransfer()
 			go func() {
@@ -279,7 +279,7 @@ func TestWatchRelease(t *testing.T) {
 }
 
 func TestWatchFinishedTransfer(t *testing.T) {
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, _ <-chan struct{}, _ chan<- struct{}) transfer {
 			xfer := newTransfer()
 			go func() {
@@ -321,7 +321,7 @@ func TestDuplicateTransfer(t *testing.T) {
 
 	var xferFuncCalls int32
 
-	makeXferFunc := func(id string) DoFunc {
+	makeXferFunc := func(id string) doFunc {
 		return func(progressChan chan<- progress.Progress, _ <-chan struct{}, _ chan<- struct{}) transfer {
 			atomic.AddInt32(&xferFuncCalls, 1)
 			xfer := newTransfer()
diff --git a/distribution/xfer/upload.go b/distribution/xfer/upload.go
index 9f870afb6e..40705bad6c 100644
--- a/distribution/xfer/upload.go
+++ b/distribution/xfer/upload.go
@@ -102,7 +102,7 @@ func (lum *LayerUploadManager) Upload(ctx context.Context, layers []UploadDescri
 	return nil
 }
 
-func (lum *LayerUploadManager) makeUploadFunc(descriptor UploadDescriptor) DoFunc {
+func (lum *LayerUploadManager) makeUploadFunc(descriptor UploadDescriptor) doFunc {
 	return func(progressChan chan<- progress.Progress, start <-chan struct{}, inactive chan<- struct{}) transfer {
 		u := &uploadTransfer{
 			transfer: newTransfer(),