I cannot get ZwFsControlFile()to return Lcn?s on a FSCTL_GET_RETRIEVAL_POINTERS call. It keeps returning 0.
In UM, I execute the following and get the values shown, and I have confirmed they are correct by examining the raw disk:
hFile= CreateFile(L"r:\Test.txt", FILE_READ_DATA, 0, NULL,
OPEN_EXISTING, 0, NULL);
BOOL bRetval= DeviceIoControl(hFile,
FSCTL_GET_RETRIEVAL_POINTERS, &startingVcn,
sizeof(startingVcn), pRerievalPointers,
cbRerievalPointers, &dwBytesReturned, NULL);
DeviceIoControl() returns TRUE, with dwBytesReturned=0x20 and the following values in pRerievalPointers:
ExtentCount: 1
StartingVcn: 0
Extents[0].NextVcn: 0x4
Extents[0].Lcn: 0x7242E
However, in KM, ZwFsControlFile() returns zero (0) for pRerievalPointers->Extents.Lcn
InitializeObjectAttributes(&ObjAttribs, & UnicodeFileName,
OBJ_KERNEL_HANDLE, NULL, NULL);
ntStatus= IoCreateFile(&hFile, FILE_ALL_ACCESS, &ObjAttribs,
&IoStatusBlock, NULL, 0, 0, FILE_OPEN, 0, NULL, 0,
CreateFileTypeNone, NULL,
IO_NO_PARAMETER_CHECKING);
ntStatus= ZwFsControlFile(hFileStream, NULL, NULL, NULL,
&IoStatusBlock,
FSCTL_GET_RETRIEVAL_POINTERS,
&startingVcn, sizeof(startingVcn),
pRerievalPointers, cbRerievalPointers);
ZwFsControlFile() returns STATUS_SUCCESS, with IoStatusBlock.Information=0x20 and the following values in pRerievalPointers:
ExtentCount: 1
StartingVcn: 0
Extents[0].NextVcn: 0x4
Extents[0].Lcn= 0 **** NOTE 0
The test data file (r:\Test.tx) is not compressed and is not sparse. It is a file with normal attributes. It resides on an NTFS (3.1) volume. The file is overr 1KB and the data attribute is not resident. I appreciate your thoughts. Thank you.