Date: Sat, 5 Oct 2002 09:54:41 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Robert Watson <rwatson@FreeBSD.ORG> Cc: Terry Lambert <tlambert2@mindspring.com>, Emiel Kollof <coolvibe@hackerheaven.org>, Peter Wemm <peter@wemm.org>, Poul-Henning Kamp <phk@critter.freebsd.dk>, n0go013 <ttz@blahdeblah.demon.co.uk>, current <freebsd-current@FreeBSD.ORG> Subject: Re: [ GEOM tests ] disklabel warnings and vinum drives lost Message-ID: <20021005002441.GS72541@wantadilla.lemis.com> In-Reply-To: <Pine.NEB.3.96L.1021004201933.64999K-100000@fledge.watson.org> References: <Pine.NEB.3.96L.1021004200338.70577U-100000@fledge.watson.org> <Pine.NEB.3.96L.1021004201933.64999K-100000@fledge.watson.org>
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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 <mux@FreeBSD.org> 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
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