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Date: Mon, 24 Jul 1995 15:35:04 +0100 (BST)
From: Doug Rabson <dfr@render.com>
To: Matt Dillon <dillon@blob.best.net>
cc: bugs@freebsd.org
Subject: Re: Here's a new one: /bin/mv truncates destination if dest is NFS
In-Reply-To: <199507221649.JAA11816@blob.best.net>
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On Sat, 22 Jul 1995, Matt Dillon wrote:

>     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.

I just fixed this in -current.  You can either get a new copy of 
nfs_vnops.c or apply this patch:

Index: nfs_vnops.c
===================================================================
RCS file: /home/ncvs/src/sys/nfs/nfs_vnops.c,v
retrieving revision 1.20
diff -c -r1.20 nfs_vnops.c
*** 1.20	1995/07/13 17:55:12
--- nfs_vnops.c	1995/07/24 11:52:16
***************
*** 620,626 ****
  		return (error);
  	error = nfs_setattrrpc(vp, vap, ap->a_cred, ap->a_p);
  	if (error) {
! 		np->n_size = np->n_vattr.va_size = tsize;
  		vnode_pager_setsize(vp, (u_long)np->n_size);
  	}
  	return (error);
--- 620,627 ----
  		return (error);
  	error = nfs_setattrrpc(vp, vap, ap->a_cred, ap->a_p);
  	if (error) {
! 		if (vap->va_size != VNOVAL)
! 			np->n_size = np->n_vattr.va_size = tsize;
  		vnode_pager_setsize(vp, (u_long)np->n_size);
  	}
  	return (error);


--
Doug Rabson, Microsoft RenderMorphics Ltd.	Mail:  dfr@render.com
						Phone: +44 171 251 4411
						FAX:   +44 171 251 0939