refactor

weed/filesys/dirty_pages.go

@@ -0,0 +1,8 @@
+package filesys
+
+type DirtyPages interface {
+	AddPage(offset int64, data []byte)
+	FlushData() error
+	ReadDirtyDataAt(data []byte, startOffset int64) (maxStop int64)
+	GetStorageOptions() (collection, replication string)
+}