diff --git a/weed/filesys/page_writer.go b/weed/filesys/page_writer.go
index 02b5f1f35..1547bce26 100644
--- a/weed/filesys/page_writer.go
+++ b/weed/filesys/page_writer.go
@@ -84,7 +84,7 @@ func (pw *PageWriter) ReadDirtyDataAt(data []byte, offset int64) (maxStop int64)
 		data = data[readSize:]
 	}
 
-	checkByteZero("page writer read", p, 0, maxStop-offset)
+	page_writer.CheckByteZero("page writer read", data, 0, maxStop-offset)
 
 	return
 }
diff --git a/weed/filesys/page_writer/chunked_file_writer.go b/weed/filesys/page_writer/chunked_file_writer.go
index 948547878..73792a00e 100644
--- a/weed/filesys/page_writer/chunked_file_writer.go
+++ b/weed/filesys/page_writer/chunked_file_writer.go
@@ -73,7 +73,7 @@ func (cw *ChunkedFileWriter) ReadDataAt(p []byte, off int64) (maxStop int64) {
 					glog.Errorf("reading temp file: %v", err)
 					break
 				}
-				checkByteZero("temp file writer read", p, logicStart-off, logicStop-off)
+				CheckByteZero("temp file writer read", p, logicStart-off, logicStop-off)
 				maxStop = max(maxStop, logicStop)
 			}
 		}
diff --git a/weed/filesys/page_writer/chunked_stream_writer.go b/weed/filesys/page_writer/chunked_stream_writer.go
index a38193131..bd3dd4a45 100644
--- a/weed/filesys/page_writer/chunked_stream_writer.go
+++ b/weed/filesys/page_writer/chunked_stream_writer.go
@@ -81,7 +81,7 @@ func (cw *ChunkedStreamWriter) ReadDataAt(p []byte, off int64) (maxStop int64) {
 			copy(p[logicStart-off:logicStop-off], memChunk.buf[logicStart-memChunkBaseOffset:logicStop-memChunkBaseOffset])
 			maxStop = max(maxStop, logicStop)
 
-			checkByteZero("stream writer read", p, logicStart-off, logicStop-off)
+			CheckByteZero("stream writer read", p, logicStart-off, logicStop-off)
 
 		}
 	}
diff --git a/weed/filesys/page_writer/debug_content.go b/weed/filesys/page_writer/debug_content.go
index 2e5734ced..f6913ed26 100644
--- a/weed/filesys/page_writer/debug_content.go
+++ b/weed/filesys/page_writer/debug_content.go
@@ -2,7 +2,7 @@ package page_writer
 
 import "github.com/chrislusf/seaweedfs/weed/glog"
 
-func checkByteZero(message string, p []byte, start, stop int64) {
+func CheckByteZero(message string, p []byte, start, stop int64) {
 	isAllZero := true
 	for i := start; i < stop; i++ {
 		if p[i] != 0 {