From owner-freebsd-current@FreeBSD.ORG  Fri Oct  7 19:03:55 2011
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 35E5E1065670
	for <freebsd-current@freebsd.org>; Fri,  7 Oct 2011 19:03:55 +0000 (UTC)
	(envelope-from phk@phk.freebsd.dk)
Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222])
	by mx1.freebsd.org (Postfix) with ESMTP id E9A5E8FC17
	for <freebsd-current@freebsd.org>; Fri,  7 Oct 2011 19:03:54 +0000 (UTC)
Received: from critter.freebsd.dk (critter.freebsd.dk [192.168.61.3])
	by phk.freebsd.dk (Postfix) with ESMTP id 937C25DA8;
	Fri,  7 Oct 2011 19:03:53 +0000 (UTC)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
	by critter.freebsd.dk (8.14.5/8.14.5) with ESMTP id p97J3qct081392;
	Fri, 7 Oct 2011 19:03:52 GMT (envelope-from phk@phk.freebsd.dk)
To: Warren Block <wblock@wonkity.com>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Fri, 07 Oct 2011 12:53:22 CST."
	<alpine.BSF.2.00.1110071236270.2450@wonkity.com>
Content-Type: text/plain; charset=ISO-8859-1
Date: Fri, 07 Oct 2011 19:03:52 +0000
Message-ID: <81391.1318014232@critter.freebsd.dk>
Cc: freebsd-current@freebsd.org, Benjamin Kaduk <kaduk@mit.edu>,
	Arnaud Lacombe <lacombar@gmail.com>
Subject: Re: aliasing (or renaming) kern.geom.debugflags
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: Fri, 07 Oct 2011 19:03:55 -0000

In message <alpine.BSF.2.00.1110071236270.2450@wonkity.com>, Warren Block write
s:

>>>> Which is the exactly right question to ask.
>>>>
>>>> The procedure documented is clearly flawed.
>>>
>
>Well, yes.  The goal is to unprotect the device, regardless of what may 
>already be on it.  Then the user can overwrite it with the memory stick 
>image.

Unprotect from what ?  from being already mounted ?

If you cannot open a geom provider for writing, then it is because
some piece of code in the kernel thinks it already owns the device
and don't want you to muck about with it.

Overriding this check is just asking for panics...


What I usually do in cases like this is:

	(umount /dev/${whatever} || true) > /dev/null 2>&1

And if that isn't enough, or not possible, then the user needs
to undo whatever he did to the device...


-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.