From owner-freebsd-current Fri Oct 4 17:24:46 2002 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 140C137B401; Fri, 4 Oct 2002 17:24:45 -0700 (PDT) Received: from wantadilla.lemis.com (wantadilla.lemis.com [192.109.197.80]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7FCAC43E42; Fri, 4 Oct 2002 17:24:43 -0700 (PDT) (envelope-from grog@lemis.com) Received: by wantadilla.lemis.com (Postfix, from userid 1004) id 8370A81441; Sat, 5 Oct 2002 09:54:41 +0930 (CST) Date: Sat, 5 Oct 2002 09:54:41 +0930 From: Greg 'groggy' Lehey To: Robert Watson Cc: Terry Lambert , Emiel Kollof , Peter Wemm , Poul-Henning Kamp , n0go013 , current Subject: Re: [ GEOM tests ] disklabel warnings and vinum drives lost Message-ID: <20021005002441.GS72541@wantadilla.lemis.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4i Organization: The FreeBSD Project Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.FreeBSD.org/ X-PGP-Fingerprint: 9A1B 8202 BCCE B846 F92F 09AC 22E6 F290 507A 4223 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Friday, 4 October 2002 at 20:21:29 -0400, Robert Watson wrote: > > On Fri, 4 Oct 2002, Robert Watson wrote: > >> On Fri, 4 Oct 2002, Terry Lambert wrote: >> >>> The assumption here is that the devfs will be available to the system >>> before the root is mounted transparently over it. This is also doable >>> with an unmounted instance of the backing devfs, not yet mounted on >>> /dev, if a transparent mount of / over top of a preexiting / -> /dev is >>> not supported (i.e. devfs is mounted on /dev on the root FS, rather than >>> the root FS being mounted on a backing node on which defvfs is already >>> mounted on /, and the devices showing through as if they were on /). >> >> Actually, no -- Vinum doesn't know how to do that--the device name used >> in this code originates in a userland ioctl() configuration call for >> Vinum. However, here's a patch that makes Vinum use namei() to rely on >> devfs to locate requested devices instead of parsing the device name and >> guessing the device number (incorrectly with GEOM). Unfortunately, I >> almost immediately run into a divide by zero due to a zero sector size. >> Jeff Roberson mentioned to me he had a fix for this bug that he sent to >> Greg, but that was never committed. > > On the general topic of access to devices before a root has been found, > Maxime Henrion has done some interesting work on > 'rootfs', a pseudofs used to bootstrap support for devfs, etc. In such an > environment, Vinum and other consumers of devices would be able to rely on > devfs access prior to the "real root" mount process. I'm not sure which > pivotroot-like trick he's using, or whether he's doing the union thing to > do the root re-mount. Presumably he has to be careful not to deadfs the > devfs nodes in place before the real root turns up, etc. As I say, it was working in early 2000. Some details needed changing, and the work never got finished, but it wasn't very much work. Greg -- See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message