From owner-freebsd-current@FreeBSD.ORG  Tue May  3 11:25:55 2005
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 9AB6E16A4CE
	for <freebsd-current@freebsd.org>;
	Tue,  3 May 2005 11:25:55 +0000 (GMT)
Received: from asterix.rsu.ru (asterix.rsu.ru [195.208.245.250])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 995EE43D2D
	for <freebsd-current@freebsd.org>;
	Tue,  3 May 2005 11:25:54 +0000 (GMT)	(envelope-from os@rsu.ru)
Received: from os.adsl.r61.net (os@os.adsl.r61.net [195.208.243.95])
	(authenticated bits=0)
	by asterix.rsu.ru (8.13.3/8.13.3) with ESMTP id j43BPW0W092507
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT);
	Tue, 3 May 2005 15:25:32 +0400 (MSD)
	(envelope-from os@rsu.ru)
Date: Tue, 3 May 2005 15:25:36 +0400 (MSD)
From: Oleg Sharoiko <os@rsu.ru>
To: Jeff Roberson <jroberson@chesapeake.net>
In-Reply-To: <20050501061323.X71837@mail.chesapeake.net>
Message-ID: <20050503151131.R787@localhost>
References: <E1DS8Gs-000OTa-1Y@cs1.cs.huji.ac.il>
	<20050501034520.N71837@mail.chesapeake.net>
	<20050501061323.X71837@mail.chesapeake.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Virus-Scanned: ClamAV version 0.81, clamav-milter version 0.81b on
	asterix.rsu.ru
X-Virus-Status: Clean
X-Spam-Status: No, score=-5.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 
	autolearn=ham version=3.0.2
X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on asterix.rsu.ru
X-Mailman-Approved-At: Tue, 03 May 2005 11:42:11 +0000
cc: freebsd-current@freebsd.org
cc: Kris Kennaway <kris@obsecurity.org>
Subject: Re: diskless/unionfs panics 
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 03 May 2005 11:25:55 -0000


On Sun, 1 May 2005, Jeff Roberson wrote:

JR>Yes, unfortunately this is only part of the problem.  The v_object can
JR>change on a unionfs vnode leading to inconsistent results for mmap/exec.
JR>This also causes problems for unionfs mounted on top of unionfs as the
JR>lower vp can also change v_object fields.  This was one advantage to the
JR>VOP based solution.  It would propagate all the way down the stack on each
JR>access.

So do I get it right that the problems can happen if file being execed or 
mmaped over unionfs will at the same time be changed on ufs (assuming that 
ufs was used to mount unionfs)? Does this mean that nullfs also have the same 
problem? But how can this problem be solved? And what is VOP based solution?

-- 
Oleg Sharoiko.
Software and Network Engineer
Computer Center of Rostov State University.