From owner-freebsd-current  Sun Jun 17 11:47:14 2001
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To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc: Jens Schweikhardt <schweikh@schweikhardt.net>,
	FreeBSD current <freebsd-current@FreeBSD.ORG>
Subject: Re: mdconfig/umount Fatal trap 12 
In-Reply-To: <73794.992802614@critter>; from phk@critter.freebsd.dk on "Sun, 17 Jun 2001 20:30:14 +0200"
Date: Sun, 17 Jun 2001 11:46:57 -0700
From: Dima Dorfman <dima@unixfreak.org>
Message-Id: <20010617184657.1503D3E0B@bazooka.unixfreak.org>
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Poul-Henning Kamp <phk@critter.freebsd.dk> writes:
> In message <20010617181041.7153C3E0B@bazooka.unixfreak.org>, Dima Dorfman writes:
> >Jens Schweikhardt <schweikh@schweikhardt.net> writes:
> >> hello, world\n
> >> 
> >> with a system cvsupped June 6th I can reliably reproduce a
> >> [panic]
> >> when I try to unmount a deleted mdconfig device. Here's the recipe:
> >> 
> >> # file iso is a Freebsd 4.3 Wind River CD image made with
> >> # dd if=/dev/cd0c of=file.iso bs=2048
> >> 
> >> 	mdconfig -a -t vnode -f file.iso
> >> 	mount -t cd9660 /dev/md0 /mnt/freebsd-cd
> >> 	mdconfig -d -u md0
> >> 	umount /dev/md0
> >> 
> >> I'm not sure if this is the right fix but what about having the
> >> mdconfig -d fail with EBUSY in case someone tries to delete a mounted
> >> md device?
> >
> >Been there, done that.  Got the patches and long thread(s) to prove it
> >;-).  See message ID 20010313071744.C988C3E09@bazooka.unixfreak.org.
> 
> The idea here is that md(4) should be able to simulate a media which
> disappears with no warning so that people can debug problems related
> to (too) dynamic media transitions.

Right.  I agree with your assessment in the thread I mentioned above.
My apologies if I made it sound derogatory.

> If people think this is too much of a panic(8) implementation we
> can hide this behaviour behind a -JUSTDOIT! option.

This is easy to do; just add an -f option to mdconfig (which can be
converted into an MD_FORCE flag or something) which means "bypass as
many sanity checks as possible".  I'll do the work if it's desired.

Regards,

					Dima Dorfman
					dima@unixfreak.org

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