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 <[EMAIL PROTECTED]> 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 [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
