哪位大侠订阅过OSR上的NT insider(2002.4)，我需要上面的一篇文章？

我在OSR上看到，NT insider（2002.4)上有一篇文章，介绍在文件过滤器中如何跟踪引用计数的问题，我不能下载这篇文章，不知哪位大侠有这篇文章，能否共享一下，不胜感激。

Tracking State and Context - Reference Counting for File System Filter Drivers
The NT Insider, Vol 9, Issue 2, Mar-Apr 2002 | Published: 15-Apr-02| Modified: 06-May-03



One of the challenges for a file systems filter driver in the Windows NT, 2000 or XP environment is knowing precisely when it is “OK” to discard per-file state information.  While it is customary for file system filter drivers to track such state based on the FsContext field of the FILE_OBJECT, the new file system filter driver writer may be frustrated to find that some I/O operations are missed.

 

Analyzing this problem, it is easy to observe that matching IRP_MJ_CLOSE operations against IRP_MJ_CREATE operations is not enough to properly determine when it is OK to discard the FsContext-related file state within the filter driver. We have previously described why this is the case (the use of stream file objects by the file systems) but in this article the emphasis is on describing an algorithm that allows the filter driver not to discard the state until the last reference to the file is truly gone.

 

First, it is worth reviewing the reason that reference counting is not a trivial exercise for file system filter drivers, then we’ll review the various cases that any algorithm must take into account, and finally propose our algorithm for tracking references to the per-file data normally maintained by a file system filter driver.

 

A file system has several mechanisms for creating file objects that it may use for its own internal processing.  These include IoCreateStreamFileObject, IoCreateStreamFileObjectLite, and IoCreateStreamFileObjectEx.  Not all of these are available in all versions, but even the Windows NT 4.0 IFS Kit contained the IoCreateStreamFileObject call.  Both IoCreateStreamFileObject and IoCreateStreamFileObjectLite are documented in the Windows XP IFS Kit and each provides similar functionality