Everhart, Glenn
From:	DavidJ@Charismac.com
Sent:	Monday, January 25, 1999 1:23 PM
To:	ntdev@atria.com
Subject:	[ntdev] Allocating Irps
Hi:

	I have a filter driver that sits on top of a hard drive.  I am doing
my own I/O by creating my own IRPs.  What is happening it that it is working
fine for the first 1000 Irps and then it is the blue screen of death with
the error PAGE_FAULT_IN_NON_PAGED_AREA.  At first I was using IoAllocateIrp
and it was my contention that I was running out of memory and the 1000 Irp
was the culprit.  So I then allocated a block of memory in the driver entry
and set up a linked list that would allocate and free Irps to the list.
This did not change the result at all, everytime after the 1000 Irp is sent
it would crash.  So then I thought I would set up my Irp and release it and
then just send the original one that was intercepted.  This did not change
the results on the 1000 irp it crashed.  Then just trying scenarios for no
reason I found the problem.  The problem is when I set data into the stack
locations of the Irp that I have allocated, such as MajorFunction, any of
the parameters and the device object.   Here is the following code segment
that is failing after it has been run 1000 times.  Note that what is passed
in is only the DeviceObject and the Irp.

Thanks 
David Jones




	CCHAR							buffer[32];
	PDEVICE_EXTENSION
deviceExtension;
	PIO_STACK_LOCATION
currentIrpStack;
	PIO_STACK_LOCATION
nextIrpStack;
	PIO_STACK_LOCATION
newCurrentIrpStack;
	PIO_STACK_LOCATION
newNextIrpStack;
	PIRP							currentIrp;
	PIRP							newIrp;
	NTSTATUS						status;
	
	static int						count = 1;
// Debug purposes only

	KdPrint(("I am in the write to mirror routine\n"));

	deviceExtension = (PDEVICE_EXTENSION)DeviceObject->DeviceExtension;
	currentIrpStack = IoGetCurrentIrpStackLocation( Irp );
	nextIrpStack = IoGetNextIrpStackLocation( Irp );

	nextIrpStack->Parameters.Others.Argument1 = (PVOID)1;

	newIrp = AnubisAllocateIrp( DeviceObject->StackSize, TRUE );

	if ( newIrp == NULL )
		return STATUS_BAD_DEVICE_TYPE;

	sprintf( buffer, "The Number of Irp allocated is %d\n", count );
	KdPrint((buffer));
	count++;

	newIrp->MdlAddress = Irp->MdlAddress;

	if ( count == 1000 )
		KdPrint(("Dave I am here at 1000\n"));
	
	
	IoSetNextIrpStackLocation( newIrp );

	newCurrentIrpStack = IoGetCurrentIrpStackLocation( newIrp );

	newCurrentIrpStack->MajorFunction = IRP_MJ_WRITE;
//  These four statments will cause this to fail but if commented out it
works fine
	newCurrentIrpStack->Parameters.Read.Length =
currentIrpStack->Parameters.Read.Length;
//	newCurrentIrpStack->Parameters.Read.ByteOffset =
currentIrpStack->Parameters.Read.ByteOffset;
//	newCurrentIrpStack->DeviceObject =
deviceExtension->TargetDeviceObject;


	newNextIrpStack = IoGetNextIrpStackLocation( newIrp );

	newIrp->AssociatedIrp.MasterIrp = Irp;
//	*newNextIrpStack = *newCurrentIrpStack;  // This statment will also
cause it to fail

	

	AnubisFreeIrp( newIrp );


		*nextIrpStack = *currentIrpStack;
		IoSetCompletionRoutine( Irp, WriteCompletion,
deviceExtension, TRUE, TRUE, TRUE );


		status = IoCallDriver( deviceExtension->TargetDeviceObject,
Irp );

		
		return status;

//		IoSetCompletionRoutine( newIrp,
//
IoCompleteAssociated,
//
deviceExtension,
//								TRUE,
//								TRUE,
//								TRUE );
//
//		status = IoCallDriver( deviceExtension->TargetDeviceObject,
newIrp );
//		return status;


	return STATUS_SUCCESS;


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