File cacheing problem?

[James H. Puttick]

I have a Linux box (Pentium III processor, 256M RAM) running 
kernel version 2.4.3, and smbmount version 2.0.7. The Linux box has 
a Windows 2000 Server share mounted via "mount -t smbfs ...".

I am running into what seems to be a cacheing problem. I am doing 
software development on this share, editing the files from a Win98 
workstation, and compiling on the Linux box.

However, frequently, if I edit a file, make a few small changes (so that 
the size of the file changes by a few dozen bytes or less), and then 
recompile, Linux gets a corrupt version of the file. Suppose I've 
increased the file length by 20 bytes. I will get the *old* version of the 
file, but then padded out to the correct length with 20 nullchars at the 
end.

When this happens, I've found the following seems to force Linux to 
get a correct copy: delete a big chunk of the file, save it (from 
Win98), reread it from Linux, put the big chunk back, and then reread 
it again.

I used a network sniffer to monitor the packets. What I found is that, 
when the problem occurs, Linux sends SMB requests to query the 
path info for the file and open the file, but does not actually reread the 
file.

My conclusion is that either (a) Win2K is providing Linux with the 
information indicating that the file has changed, but Linux is failing to 
recognize that it has to re-read the file, or (b) Win2K is not providing 
that information, so that Linux doesn't realize that the file has changed. 
(But it is odd that Linux *does* know that the length has changed.) 
Unfortunately, I don't know enough about SMB protocol to 
determine where the fault is.

I don't know if timestamps are relevant, but the Linux box uses NTP 
to maintain the same time as the Win2K machine; and the Win98 
machine is within a second of the same time.

Suggestions?

Also, is there a way to force SMB to dump its cache and reread the 
file, other than unmounting and remounting the share?

Thanks.

-- James


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James H. Puttick

Kerr Vayne Systems Ltd.
1 Valleywood Drive, Unit 5A
Markham, Ontario L3R 5L9
Canada

+1 905 475 6161  office
+1 905 479 9833  fax

mailto:james.puttick at kvs.com
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