From owner-freebsd-current@FreeBSD.ORG  Wed Oct 14 13:35:29 2009
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 6351510656A6
	for <freebsd-current@freebsd.org>; Wed, 14 Oct 2009 13:35:29 +0000 (UTC)
	(envelope-from a_best01@uni-muenster.de)
Received: from zivm-exrelay1.uni-muenster.de (ZIVM-EXRELAY1.UNI-MUENSTER.DE
	[128.176.192.14])
	by mx1.freebsd.org (Postfix) with ESMTP id EC4B08FC31
	for <freebsd-current@freebsd.org>; Wed, 14 Oct 2009 13:35:28 +0000 (UTC)
X-IronPort-AV: E=Sophos;i="4.44,557,1249250400"; d="scan'208";a="285465774"
Received: from zivmaildisp1.uni-muenster.de (HELO
	ZIVMAILUSER01.UNI-MUENSTER.DE) ([128.176.188.85])
	by zivm-relay1.uni-muenster.de with ESMTP; 14 Oct 2009 15:35:27 +0200
Received: by ZIVMAILUSER01.UNI-MUENSTER.DE (Postfix, from userid 149459)
	id 4C2141B0766; Wed, 14 Oct 2009 15:35:27 +0200 (CEST)
Date: Wed, 14 Oct 2009 15:35:26 +0200 (CEST)
From: Alexander Best <alexbestms@math.uni-muenster.de>
Sender: <a_best01@uni-muenster.de>
Organization: Westfaelische Wilhelms-Universitaet Muenster
To: Andriy Gapon <avg@icyb.net.ua>
Message-ID: <permail-20091014133526f0889e840000348b-a_best01@message-id.uni-muenster.de>
In-Reply-To: <4AD5BD00.4050700@icyb.net.ua>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: freebsd-current@FreeBSD.org
Subject: Re: panic when mounting device >= 2 times
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
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: Wed, 14 Oct 2009 13:35:29 -0000

Andriy Gapon schrieb am 2009-10-14:
> on 14/10/2009 14:21 Alexander Best said the following:
> > could somebody have a look at this PR please:
> > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/108968

> > this still exists in -CURRENT.

> This is because of serious and long-standing brokenness (probably
> from time of
> introduction of GEOM) in g_vfs_open/g_vfs_close.
> The essence:
> 1. we allow multiple concurrent read-only mounts of a device
> 2. but even a read-only mount mangles bufobj of device vnode
> 3. Bug!
> Trivial fix with POLA violation - prohibit concurrent RO mounts.
> Non-trivial fix - _somehow_ avoid changing or depending on device
> vnode bufobj.

> See this for even more evil example of this problem:
> http://lists.freebsd.org/pipermail/freebsd-fs/2009-February/005676.html

thanks a lot for the hint. unfortunately i'm not a programmer and thus won't
be able to help with this problem. :-(

cheers.
alex