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To: Matt Dillon <dillon@best.net>, freebsd-bugs@FreeBSD.ORG,
        thepish@dana.clari.net.au
Subject: Re: kern/7596: serious data integrity problem when reading WHILE writing NFSv3 client-end 
In-Reply-To: Your message of "Thu, 13 Aug 1998 11:24:11 PDT."
             <199808131824.LAA02830@flea.best.net> 
Date: Thu, 13 Aug 1998 14:41:15 -0700
From: Mika Nystroem <mika@cs.caltech.edu>
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Matt Dillon writes:
>:Peter Hawkins writes:
>:>See also PR 7418 - the plot thickens...
...
>:Sure, I normally run these applications against a FreeBSD NFS server
>:with a four-way CCD, but this particular case was on a Slowaris
>:2.5 (sparcstation 1) machine with perfectly standard UFS.  I haven't
>:been able to exhibit it on a local FFS disk.  I also haven't been
>:able to exhibit it with a NetBSD NFS client, which is a bit odd
>:because all the code that my untrained eye found in /sys/nfs that
>:looked suspicious was the same on NetBSD and FreeBSD :)
>:
>:  Mika
>:  <mika@cs.caltech.edu>
>
>    I'm not sure in what circumstances you are seeing the problem.  You
>    are seeing it locally on a sun and on a sun client with a FreeBSD NFS
>    server?  Is the file corrupted on the FreeBSD NFS server itself when you
>    access it locally?
>
>						-Matt
>

Sorry, I should have included more details from the original PR
#7596.  This is a *client*-end NFSv3 problem in FreeBSD, that much
I am pretty sure of.  Both the reading and writing processes are
on the same NFS client machine.  I'm using a FreeBSD NFSv3 client
here, and the problem appears with NFS v3 servers from Solaris,
FreeBSD, and NetBSD.  Yes, the file is corrupted on the server's
disk.  The problem does not appear with FFS or NFSv2 or MFS. My
uneducated guess is that it has something to do with v3's write
buffering, but the NFS code is really quite hard to understand.

   Mika

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