I have requirement to support 128 bit file ID's for ReFS volumes. I am calling FltQueryInformationFile once with FILE_INTERNAL_INFORMATION and again with FILE_ID_INFORMATION to retrieve both the 64 and 128 bit file ID's. I thought the 64 bit file ID would be useless but to my surprise I was able to open the file using FileTest. The 128 bit one works too.
I guess the first question is, how come the 64 bit file ID works? The second question, is the 128 bit one still needed?