I am writing a windows filesystem minifilter driver that must fail IRP's in a preoperation callback.
How can I find out from the callback parameters if the operation is read-like ( only reads data ) or it's write-like ( modifies data on the disk - write, delete etc ) ?

I'm thinking on:

Data->Iopb->TargetFileObject->ReadAccess 
Data->Iopb->TargetFileObject->WriteAccess 

But I'm not sure, I think thees are available only in postoperation callback. The documentation is really cumbersome.

Code sample:

FLT_PREOP_CALLBACK_STATUS
Fail (
    __inout PFLT_CALLBACK_DATA Data,
    __in PCFLT_RELATED_OBJECTS FltObjects,
    __deref_out_opt PVOID *CompletionContext
    )
{
    FLT_PREOP_CALLBACK_STATUS status = FLT_PREOP_SUCCESS_NO_CALLBACK;

    if ( IS WRITE_LIKE(Data, FltObjects)  ) { // ??? HOW DO I FIND OUT????

        if( FLT_IS_FASTIO_OPERATION(Data) ){
            status = FLT_PREOP_DISALLOW_FASTIO;
        } else {
            status = FLT_PREOP_COMPLETE;
        }
        Data->IoStatus.Status = STATUS_ACCESS_DENIED;
        Data->IoStatus.Information = 0;
        return status;

    }
    return status;
}