From owner-freebsd-current@FreeBSD.ORG  Sat Sep 26 07:21:59 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 E71A01065676;
	Sat, 26 Sep 2009 07:21:59 +0000 (UTC) (envelope-from dfr@rabson.org)
Received: from itchy.rabson.org (router.rabson.org [80.177.232.241])
	by mx1.freebsd.org (Postfix) with ESMTP id A343C8FC17;
	Sat, 26 Sep 2009 07:21:59 +0000 (UTC)
Received: from [IPv6:2001:470:909f:1:225:ff:feed:9426] (unknown
	[IPv6:2001:470:909f:1:225:ff:feed:9426])
	by itchy.rabson.org (Postfix) with ESMTP id 8F9E15D12;
	Sat, 26 Sep 2009 08:21:27 +0100 (BST)
Mime-Version: 1.0 (Apple Message framework v1076)
Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes
From: Doug Rabson <dfr@rabson.org>
In-Reply-To: <ed91d4a80909251449i47d2a31dw4ebfd74f71e29dba@mail.gmail.com>
Date: Sat, 26 Sep 2009 08:21:27 +0100
Content-Transfer-Encoding: 7bit
Message-Id: <290F8258-F9F7-42C8-83EB-88266B2992E4@rabson.org>
References: <20090925154125.GD48707@roberto-al.eurocontrol.fr>
	<AE91C53E-FD74-4B6D-9498-D4F11FE5AA2E@lassitu.de>
	<ed91d4a80909251449i47d2a31dw4ebfd74f71e29dba@mail.gmail.com>
To: Artem Belevich <fbsdlist@src.cx>
X-Mailer: Apple Mail (2.1076)
Cc: Ollivier Robert <roberto@keltia.freenix.fr>, dfr@freebsd.org,
	freebsd-current@freebsd.org, Stefan Bethke <stb@lassitu.de>
Subject: Re: Booting off raidz *mostly* work
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: Sat, 26 Sep 2009 07:22:00 -0000


On 25 Sep 2009, at 22:49, Artem Belevich wrote:

> Our bootloader implementation does not know how to read gang blocks.
> Compare the code from OpenSolaris' variant of grub with what we have
> and find the differences:
>
> Search for zio_read_data here:
> http://bitbucket.org/osunix/osunix-gate/src/1cca4617b3a8/usr/src/grub/grub-0.97/stage2/fsys_zfs.c
>
> And compare with our zio_read here:
> http://fxr.watson.org/fxr/source/boot/zfs/zfsimpl.c?im=excerpts#L900
>
> We seem to be missing gang block check. That would explain why zfsboot
> works only sometimes. If all the files are written using regular
> blocks, then we're OK. However, some time later (i.e. during upgrade
> or after an edit), some data can end up written to disk in a gang
> block and that would make zfsboot choke.

This sounds plausible - I never managed to see a gang block while I  
was working on this.