update failure policy related comment

Author: wty-Bryant

feature/s3/transfermanager/api_op_DownloadDirectory.go

@@ -60,7 +60,11 @@ type GetRequestCallback interface {
 }
 
 // DownloadDirectoryFailurePolicy is a callback to allow users to control the
-// download behavior when there are failed objects. It is invoked for every failed object
+// download behavior when there are failed objects. It is invoked for every failed object.
+// If the OnDownloadFailed returns non-nil error, downloader will cancel all ongoing
+// single object download requests and terminate the download directory process, if it returns nil
+// error, downloader will count the current request as a failed object downloaded but continue
+// getting other objects.
 type DownloadDirectoryFailurePolicy interface {
 	OnDownloadFailed(*DownloadDirectoryInput, *GetObjectInput, error) error
 }
@@ -86,13 +90,9 @@ func (IgnoreDownloadFailurePolicy) OnDownloadFailed(*DownloadDirectoryInput, *Ge
 // DownloadDirectoryOutput represents a response from the DownloadDirectory() call
 type DownloadDirectoryOutput struct {
 	// Total number of objects successfully downloaded
-	// this value might not be the real number of success if user passed a customized
-	// failure policy in input
 	ObjectsDownloaded int64
 
 	// Total number of objects failed to download
-	// this value might not be the real number of failure if user passed a customized
-	// failure policy in input
 	ObjectsFailed int64
 }
 

feature/s3/transfermanager/api_op_UploadDirectory.go

@@ -62,7 +62,11 @@ type PutRequestCallback interface {
 }
 
 // UploadDirectoryFailurePolicy is a callback to allow users to control the
-// upload behavior when there are failed objects. It is invoked for every failed object
+// upload behavior when there are failed objects. It is invoked for every failed object.
+// If the OnUploadFailed returns non-nil error, uploader will cancel all ongoing
+// single object upload requests and terminate the upload directory process, if it returns nil
+// error, uploader will count the current request as a failed object downloaded but continue
+// uploading other objects.
 type UploadDirectoryFailurePolicy interface {
 	OnUploadFailed(*UploadDirectoryInput, *UploadObjectInput, error) error
 }
@@ -88,13 +92,9 @@ func (IgnoreUploadFailurePolicy) OnUploadFailed(*UploadDirectoryInput, *UploadOb
 // UploadDirectoryOutput represents a response from the UploadDirectory() call
 type UploadDirectoryOutput struct {
 	// Total number of objects successfully uploaded
-	// this value might not be the real number of success if user passed a customized
-	// failure policy in input
 	ObjectsUploaded int64
 
 	// Total number of objects failed to upload
-	// this value might not be the real number of failure is user passed a customized
-	// failure policy in input
 	ObjectsFailed int64
 }