I/O May Be Performed at the Wrong Offset with Files Larger than 4 GB

ID: Q235250

The information in this article applies to:

SYMPTOMS

Certain file read or write operations (also known as input/output, or I/O operations) may be performed at incorrect locations within a file that is larger than 4 gigabytes (GB) in size.

For this problem to occur, I/O operations must be cached and asynchronous. Unbuffered, synchronous operations are not susceptible to the problem described in this article.

This problem can occur only when two I/O operations are performed in close succession if the first operation is above the 4-GB mark and the second operation is at the same offset (modulo 4 GB), below the 4-GB mark.

For example, if the first operation is performed at offset 4,295,032,832 (0x100010000 hex) and the second is performed at offset 65,536 (0x10000 hex), the second I/O operation may actually take place at the first offset.


CAUSE

In an attempt to improve performance, the cache manager attempts to perform 32-bit operations when performing certain lookup operations. 64-bit operations are more time consuming, but are required when file offsets are large enough that they cannot be represented in 32 bits. The problem described in this article occurs because the cache manager occasionally errs and performs 32-bit arithmetic when 64-bit arithmetic is required.


RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows NT 4.0 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp
The English version of this fix should have the following file attributes or later: 

   Date      Time                 Size    File name     Platform
   -------------------------------------------------------------
   06/09/99  11:36a               948,928 Ntkrnlmp.exe  x86
   06/09/99  11:35a               928,832 Ntoskrnl.exe  x86

   06/09/99  11:36a             1,414,336 Ntkrnlmp.exe  Alpha
   06/09/99  11:34a             1,385,920 Ntoskrnl.exe  Alpha

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:
Q154871 Determining If You Are Eligible for No-Charge Technical Support


STATUS

Microsoft has confirmed this to be a problem in Windows NT 4.0.

Additional query words: 


Keywords          : kbbug4.00 kbfix4.00 
Version           : winnt:4.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: August 2, 1999