From owner-freebsd-geom@FreeBSD.ORG  Wed Oct 19 17:53:12 2005
Return-Path: <owner-freebsd-geom@FreeBSD.ORG>
X-Original-To: freebsd-geom@freebsd.org
Delivered-To: freebsd-geom@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id E20EA16A41F
	for <freebsd-geom@freebsd.org>; Wed, 19 Oct 2005 17:53:12 +0000 (GMT)
	(envelope-from andrew@djw.hu)
Received: from web.djw.hu (web.djw.hu [212.92.23.53])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 8AF1243D46
	for <freebsd-geom@freebsd.org>; Wed, 19 Oct 2005 17:53:12 +0000 (GMT)
	(envelope-from andrew@djw.hu)
Received: from filter_main.jail (filter_main.jail [127.0.1.72])
	by web.djw.hu (Postfix) with ESMTP id 84CB4A953
	for <freebsd-geom@freebsd.org>; Wed, 19 Oct 2005 19:53:11 +0200 (CEST)
Received: by web.djw.hu (Postfix, from userid 1001)
	id F2BB5A950; Wed, 19 Oct 2005 19:53:10 +0200 (CEST)
Date: Wed, 19 Oct 2005 19:53:10 +0200
From: Szalai Andras <andrew@djw.hu>
To: freebsd-geom@freebsd.org
Message-ID: <20051019175310.GC76081@web.djw.hu>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.4.2.1i
Subject: geom orphan question
X-BeenThere: freebsd-geom@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: GEOM-specific discussions and implementations
	<freebsd-geom.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-geom>,
	<mailto:freebsd-geom-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-geom>
List-Post: <mailto:freebsd-geom@freebsd.org>
List-Help: <mailto:freebsd-geom-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-geom>,
	<mailto:freebsd-geom-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 19 Oct 2005 17:53:13 -0000

Hi,

I have spent few hours trying to understand geom. The I/O
path is more or less okay, but I have problems with
the orphanization procedure.

For example, if you look into g_concat.c there is a 
g_concat_orphan function that calls g_concat_remove_disk.
In this function, gconcat

1) orphans its own provider (g_orphan_provider),
2) reset access counts (g_access), 
3) detach consumer from the lower layer provider,
4) destroy the consumer.

In order to detach the consumer (step 3) you have to be sure 
that there are no active requests (bios) between the consumer and
provider. My question is how can I guarantee that there are 
no active bios when I call g_detach?

c'ya
andrew