NTSTATUS
FatFsdRead (
IN PVOLUME_DEVICE_OBJECT VolumeDeviceObject,
IN PIRP Irp
)
/*++
Routine Description:
This is the driver entry to the common read routine for NtReadFile calls.
For synchronous requests, the CommonRead is called with Wait == TRUE,
which means the request will always be completed in the current thread,
and never passed to the Fsp. If it is not a synchronous request,
CommonRead is called with Wait == FALSE, which means the request
will be passed to the Fsp only if there is a need to block.
Arguments:
VolumeDeviceObject - Supplies the volume device object where the
file being Read exists
Irp - Supplies the Irp being processed
Return Value:
NTSTATUS - The FSD status for the IRP
--*/
{
PFCB Fcb = NULL;
NTSTATUS Status;
PIRP_CONTEXT IrpContext = NULL;
BOOLEAN TopLevel;
DebugTrace(+1, Dbg, "FatFsdRead\n", 0);
//
// Call the common Read routine, with blocking allowed if synchronous
//
FsRtlEnterFileSystem();
//
// We are first going to do a quick check for paging file IO. Since this
// is a fast path, we must replicate the check for the fsdo.
//
if (!FatDeviceIsFatFsdo( IoGetCurrentIrpStackLocation(Irp)->DeviceObject)) {
Fcb = (PFCB)(IoGetCurrentIrpStackLocation(Irp)->FileObject->FsContext);
if ((NodeType(Fcb) == FAT_NTC_FCB) &&
FlagOn(Fcb->FcbState, FCB_STATE_PAGING_FILE)) {
//
// Do the usual STATUS_PENDING things.
//
IoMarkIrpPending( Irp );
//
// If there is not enough stack to do this read, then post this
// read to the overflow queue.
//
if (IoGetRemainingStackSize() < OVERFLOW_READ_THRESHHOLD) {
KEVENT Event;
PAGING_FILE_OVERFLOW_PACKET Packet;
Packet.Irp = Irp;
Packet.Fcb = Fcb;
KeInitializeEvent( &Event, NotificationEvent, FALSE );
FsRtlPostPagingFileStackOverflow( &Packet, &Event, FatOverflowPagingFileRead );
//
// And wait for the worker thread to complete the item
//
(VOID) KeWaitForSingleObject( &Event, Executive, KernelMode, FALSE, NULL );
} else {
//
// Perform the actual IO, it will be completed when the io finishes.
//
FatPagingFileIo( Irp, Fcb );
}
FsRtlExitFileSystem();
return STATUS_PENDING;
}
}
try {
TopLevel = FatIsIrpTopLevel( Irp );
IrpContext = FatCreateIrpContext( Irp, CanFsdWait( Irp ) );
//
// If this is an Mdl complete request, don't go through
// common read.
//
if ( FlagOn(IrpContext->MinorFunction, IRP_MN_COMPLETE) ) {
DebugTrace(0, Dbg, "Calling FatCompleteMdl\n", 0 );
try_return( Status = FatCompleteMdl( IrpContext, Irp ));
}
//
// Check if we have enough stack space to process this request. If there
// isn't enough then we will pass the request off to the stack overflow thread.
//
if (IoGetRemainingStackSize() < OVERFLOW_READ_THRESHHOLD) {
DebugTrace(0, Dbg, "Passing StackOverflowRead off\n", 0 );
try_return( Status = FatPostStackOverflowRead( IrpContext, Irp, Fcb ) );
}
Status = FatCommonRead( IrpContext, Irp );
try_exit: NOTHING;
} except(FatExceptionFilter( IrpContext, GetExceptionInformation() )) {
//
// We had some trouble trying to perform the requested
// operation, so we'll abort the I/O request with
// the error status that we get back from the
// execption code
//
Status = FatProcessException( IrpContext, Irp, GetExceptionCode() );
}
if (TopLevel) { IoSetTopLevelIrp( NULL ); }
FsRtlExitFileSystem();
//
// And return to our caller
//
DebugTrace(-1, Dbg, "FatFsdRead -> %08lx\n", Status);
UNREFERENCED_PARAMETER( VolumeDeviceObject );
return Status;
}
NTSTATUS
FsRtlInitializeWorkerThread (
VOID
)
{
OBJECT_ATTRIBUTES ObjectAttributes;
HANDLE Thread;
ULONG i;
NTSTATUS Status = STATUS_SUCCESS;
//
// Create worker threads to handle normal and paging overflow reads.
//
InitializeObjectAttributes(&ObjectAttributes, NULL, 0, NULL, NULL);
for (i=0; i < 2; i++) {
//
// Initialize the FsRtl stack overflow work Queue objects.
//
KeInitializeQueue(&FsRtlWorkerQueues[i], 0);
Status = PsCreateSystemThread( &Thread,
THREAD_ALL_ACCESS,
&ObjectAttributes,
0L,
NULL,
FsRtlWorkerThread,
ULongToPtr( i ));
if (!NT_SUCCESS( Status )) {
return Status;
}
ZwClose( Thread );
}
//
// Initialize the serial workitem so we can guarantee to post items
// for paging files to the worker threads.
//
KeInitializeEvent( &StackOverflowFallbackSerialEvent, SynchronizationEvent, TRUE );
//
// Pass a NOP routine through FsRtlPostStackOverfow() in order to flush out
// any prefetchw instructions that may lie in that path. Otherwise we'll
// try to patch the prefetchw instruction when we can ill afford the stack
// space.
//
#if defined(_AMD64_)
FsRtlPostStackOverflow( NULL, NULL, FsRtlpNopStackOverflowRoutine );
FsRtlPostPagingFileStackOverflow( NULL, NULL, FsRtlpNopStackOverflowRoutine );
#endif
return Status;
}
