Can't figure out why my call to IOCTL_STORAGE_MANAGE_DATA_SET_ATTRIBUTES is failing

IOCTLFish

Ok, I am trying to learn how to use IOCTL_STORAGE_MANAGE_DATA_SET_ATTRIBUTES. I have set up a VM and I call it like this:

#include <windows.h>
#include <stdio.h>
#include <string>
#include <iostream>
#include <winnt.h>
#include <winternl.h>
#include <ntddstor.h>

int main(int argc, const char* argv[]) {

    HANDLE hDevice = CreateFile(L"\\\\.\\Physicaldrive0", 
                                GENERIC_READ | GENERIC_WRITE, 
                                FILE_SHARE_READ | FILE_SHARE_WRITE, 
                                NULL, 
                                OPEN_EXISTING, 
                                FILE_FLAG_NO_BUFFERING, 
                                NULL);

    int cf_error = 0; 
    cf_error = GetLastError();

    if (hDevice == INVALID_HANDLE_VALUE) {
        std::cout << "COULDN'T GET HANDLE"; 
        return -1;
    }

    std::cout << "Device Handle error: " << cf_error << "\n";
    std::cout << "Handle value: " << hDevice << "\n"; 

    _DEVICE_MANAGE_DATA_SET_ATTRIBUTES attributes_struct; 

    LPDWORD BytesReturned = 0; 


    int inputbufferlength = 0; 

    inputbufferlength = sizeof(DEVICE_MANAGE_DATA_SET_ATTRIBUTES) + sizeof(_DEVICE_DSM_OFFLOAD_WRITE_PARAMETERS) + sizeof(DEVICE_DATA_SET_RANGE);

    PUCHAR inputbuffer = (PUCHAR)malloc(inputbufferlength);

    PUCHAR outputbuffer = (PUCHAR)malloc(inputbufferlength);

    //RtlZeroMemory(inputbuffer, inputBufferLength);

    PDEVICE_MANAGE_DATA_SET_ATTRIBUTES dsmAttributes = (PDEVICE_MANAGE_DATA_SET_ATTRIBUTES)inputbuffer;

    PDEVICE_DSM_OFFLOAD_WRITE_PARAMETERS offload_write_parameters = NULL; 

    dsmAttributes->Size = sizeof(DEVICE_MANAGE_DATA_SET_ATTRIBUTES);

    dsmAttributes->Action = DeviceDsmAction_OffloadWrite;

    dsmAttributes->Flags = 0; 

    dsmAttributes->ParameterBlockOffset = sizeof(DEVICE_MANAGE_DATA_SET_ATTRIBUTES);

    dsmAttributes->ParameterBlockLength = sizeof(DEVICE_DSM_OFFLOAD_WRITE_PARAMETERS);


    offload_write_parameters = (PDEVICE_DSM_OFFLOAD_WRITE_PARAMETERS)((PUCHAR)dsmAttributes + dsmAttributes->ParameterBlockOffset);

    offload_write_parameters->Flags = 0;
    offload_write_parameters->TokenOffset = 0;

    dsmAttributes->DataSetRangesOffset = dsmAttributes->ParameterBlockOffset + dsmAttributes->ParameterBlockLength;
    dsmAttributes->DataSetRangesLength = sizeof(DEVICE_DATA_SET_RANGE);

    PDEVICE_DATA_SET_RANGE lbaRange = NULL;
    lbaRange = (PDEVICE_DATA_SET_RANGE)((PUCHAR)dsmAttributes + dsmAttributes->DataSetRangesOffset);
    lbaRange->StartingOffset = 0;  // not sure about this one for now 
    lbaRange->LengthInBytes = 256 * 1024 * 1024;


    int status = DeviceIoControl(
        hDevice,                                  // handle to device
        IOCTL_STORAGE_MANAGE_DATA_SET_ATTRIBUTES, // dwIoControlCode
        inputbuffer,                             // input buffer
        inputbufferlength,                      // size of the input buffer
        outputbuffer,                           // output buffer
        inputbufferlength,                      // size of the input buffer - modified to be too small!
        BytesReturned,                          // number of bytes returned
        0 //(LPOVERLAPPED) &overlapped_struct   // OVERLAPPED structure
    );

    DWORD error_num = GetLastError();

    CloseHandle(hDevice);
    std::cout << "STATUS IS: " << status << "\n"; 
    std::cout << "ERROR IS: " << error_num; 
    return 0;
}

And my problem is that it returns STATUS_INVALID_PARAMETER, which would be fine but it seems like this is being returned being something other than the IOCTL I am trying to call. I put a breakpoint on my IOCTL like this:
bp partmgr!PartitionIoctlDsm

and I breakpoint the dispatcher like this:

bp partmgr!PartitionDeviceControl

But neither gets hit by my code, ever. So maybe some other device associated with that physical device doesn't like my parameters and it never makes it to IOCTL_STORAGE_MANAGE_DATA_SET_ATTRIBUTES or the associated dispatch handler. I am a little new to debugging these file system drivers so I wouldn't know where to start figuring out where to look. I cribbed some of this code off an old MS tool I found at https://github.com/microsoft/StorScore/blob/7cbe261a7cad74f3a4f758c2b8a35ca552ba8dde/src/StorageTool/src/_backup.c so I was surprised this code didn't work.

How do I debug this? Do you see anything obviously wrong with my code?