From: Dan Partelly [dan_partelly@rdsor.ro]
Sent: Saturday, June 01, 2002 8:31 PM
To: NT Developers Interest List
Subject: [ntdev] RE: ZwFlushBuffersFile from kernel

Max, thank you for giving source code. I suggested handocded IRP from my
first post . The only thing you forgot here is aquiring the file object
lock, if required, for this code to be a perfect replacemnt of the original
syscall. However, the whole discution wanst whithout a scope. Ppl shoul
understand then they try to use "exotic" techniques, they have to be aware
of OS mechanics, CPU architectures, and carefully double check the design.

My reagrds, Dan

----- Original Message -----
From: "Maxim S. Shatskih" <maxim@storagecraft.com>
To: "NT Developers Interest List" <ntdev@lists.osr.com>
Sent: Sunday, June 02, 2002 1:19 AM
Subject: [ntdev] RE: ZwFlushBuffersFile from kernel


> > youll call into the instance of ntdll.dll mapped into the current
> process
>
> In fact, the discussion started from calling the flush function of the
> FSD from the kernel.
> No need to call ntdll for this. I'm publishing a snippet of the
> debugged code which does this:
>
> // Flushes the volume
> static NTSTATUS FlushVolume(PDEVICE_OBJECT DeviceObject, PFILE_OBJECT
> FileObject)
> {
>     PIRP Irp;
>     PIO_STACK_LOCATION NextLoc;
>     NTSTATUS Status;
>     // Allocate the IRP
>     Irp = IoAllocateIrp((CCHAR)(DeviceObject->StackSize + 1), FALSE);
>     if( Irp == NULL )
>         // Failed
>         return STATUS_INSUFFICIENT_RESOURCES;
>     // Fill the IRP
>     NextLoc = IoGetNextIrpStackLocation(Irp);
>     NextLoc->MajorFunction = IRP_MJ_FLUSH_BUFFERS;
>     NextLoc->FileObject = FileObject;
>     // Pass down
>     Status = CallDriverSync(DeviceObject, Irp);
>     // Free the IRP
>     IoFreeIrp(Irp);
>     // Done
>     return Status;
> }
>
> // CallDriverSync
> // Calls the lower driver and wait for the operation to be completed
> by the lower driver
> static NTSTATUS CallDriverSync(PDEVICE_OBJECT DeviceObject, PIRP Irp)
> {
>  NTSTATUS ntStatus;
>  KEVENT event;
>  // Initialize the completion event.
>     KeInitializeEvent(&event, NotificationEvent, FALSE);
>  // Set completion routine for this request.
>     IoSetCompletionRoutine(Irp, SyncComplete, &event, TRUE, TRUE,
> TRUE);
>  // Call the target driver.
>     if ((ntStatus = IoCallDriver(DeviceObject, Irp)) ==
> STATUS_PENDING)
>     {
>         // Wait for the request to complete.
>         KeWaitForSingleObject(&event, Executive, KernelMode, FALSE,
> NULL);
>         // Update the local status.
>         ntStatus = Irp->IoStatus.Status;
>     }
>  return ntStatus;
> }
>
> // Generic completion routine to synchronize a request.
> static NTSTATUS SyncComplete(PDEVICE_OBJECT DeviceObject, PIRP Irp,
> PVOID Context)
> {
>     // Check for a Context pointer.
>  if (ARGUMENT_PRESENT(Context))
>         // Signal the IRP originator that this operation is complete.
>   KeSetEvent((PKEVENT)Context, IO_NO_INCREMENT, FALSE);
>  // Halt completing the IRP and return.
>  return STATUS_MORE_PROCESSING_REQUIRED;
>  UNREFERENCED_PARAMETER(DeviceObject);
>  UNREFERENCED_PARAMETER(Irp);
> }
>
>     Max
>
>
>
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