delete the folder and redirection

hi,
Recently,I redirect C:\c_folder to D:\d_folder in my filter driver.
the file in c_folder can be deleted,for example I can delete C:\c_folder\c_file.txt. But I can’t delete the folder in c_folder( C:\c_folder\folder),and the message is like this “this folder is using”.
In IRP_MJ_SET_INFORMATION,I found nothing different.
please give me a hint.
zhou