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Date: Sat, 22 Jul 1995 09:49:33 -0700
From: Matt Dillon <dillon@blob.best.net>
Message-Id: <199507221649.JAA11816@blob.best.net>
To: bugs@freebsd.org
Subject: Here's a new one: /bin/mv truncates destination if dest is NFS
Sender: bugs-owner@freebsd.org
Precedence: bulk

    Here's another one... /bin/mv truncates the destination file if
    the destination is an NFS filesytem.

    * Create a 24254 byte file
    * as root, chgrp the file to a group the user has no permissions on
    * as the user, /bin/mv file dest

    where dest is on an NFS mount.

    What happens is that the fchown() that /bin/mv does blows away the 
    last dirty buffer from the filecopy (which used 8K chunks) that /bin/mv
    did, so the output file winds up being only 16K long!!

    This only occurs when fchown() fails due to not being able to transfer
    the group permissions to the destination file, i.e. when you get:

    mv2: /home/au/z: set owner/group: Operation not permitted

    If I put a sleep() in just before the fchown() and manually /bin/sync
    after the file is written but before the fchown(), the file size comes
    out properly.


					-Matt