Date: Sun, 14 Dec 2003 08:57:49 -0700 From: Scott Long <scottl@freebsd.org> To: Don Lewis <truckman@freebsd.org> Cc: alc@freebsd.org Subject: Re: HAVE TRACE & DDB Re: FreeBSD 5.2-RC1 released Message-ID: <3FDC887D.9060605@freebsd.org> In-Reply-To: <200312140716.hBE7G8eF064492@gw.catspoiler.org> References: <200312140716.hBE7G8eF064492@gw.catspoiler.org>
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Don Lewis wrote:
> Following up to myself ...
>
> It looks like we're trying to recycle this vnode because of the
> following sysinstall code, in distExtractTarball():
>
> if (is_base && RunningAsInit && !Fake) {
> unmounted_dev = 1;
> unmount("/dev", MNT_FORCE);
> } else
> unmounted_dev = 0;
>
> I'm guessing that the purpose of this code is to unmount devfs from /dev
> so that when the base distribution is unpacked it can populate /dev from
> the tarball. This seems wrong, because it looks like the root file
> system is mounted on /mnt, and devfs is also mounted on /mnt/dev ...
>
> What happens if we forceably umount /dev while /dev/whatever holds a
> mounted file system? It looks like this is handled by vgonechrl(). It
> looks to me like vclean() is going to do some scary stuff to this vnode.
>
As Jeff pointed out, vfs_subr.c rev 1.461 might be the immediate problem
here. However, I can't believe that umounting devfs while it is in use
can possibly be the right thing to do. Does devfs have to be mounted in
the /mnt? Is it a chroot issue?
> BTW, I think the root vnode is the root of the md file system, not the
> root of the file system being populated by sysinstall. I don't know why
> there would be anything to sync at this point, though.
>
> I suspect that removing the above sysinstall code will fix the immediate
> problem, but there is still much I don't understand.
Removing this code will likely result in sysinstall reporting errors to
the user about not being able to unpack the files into /dev. Or even
worse, it might succeed and temporarily replace the valid entries with
invalid ones.
Scott
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