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Date:      Thu, 18 Jun 1998 22:12:17 +0200
From:      Stefan Eggers <seggers@semyam.dinoco.de>
To:        aw1@stade.co.uk
Cc:        freebsd-bugs@FreeBSD.ORG, seggers@semyam.dinoco.de
Subject:   Re: bin/5134: cdcontrol will eject a mounted CDROM 
Message-ID:  <199806182012.WAA28312@semyam.dinoco.de>
In-Reply-To: Your message of "Tue, 16 Jun 1998 01:27:48 BST." <19980616012748.D16444@stade.co.uk> 

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> >     panic: vref used where vget required
> 
> Hmm. I get the same panic if I leave a CDROM mounted in what
> I increasingly suspect is a dying drive. Sooner of later the system
> crashes this way.

Do the crashes only occur when the CD is mounted but were never
accessed since?  Or does it even occur if you used it after mounting?
If they occur in both cases then there is probably some other problem
or for some reason my machine acted different.

> How is the kernel supposed to handle a transfer error on a CDROM drive?

As any other file system.  Report the problem in a reasonable way and
doing the necessary cleanup before returning.  A panic definitely is
not a good idea.  The one happening is particularly bad as it even is
not related to some read/transfer error reporting.  It surely was
planned not to do that.  ;-)

At present it seems to have trouble with the case of read errors in
the stat operation as I found out from the crash dump.  Doing a stat
on the CD w/o it being accessible leads to a panic if nobody else has
accessed the drive before it seems.

My suggested fix is surely not the right one to do but if my theory is
right it at least stops the panics until someone with enough
experience finds out who forgot to do a VGET(9).

Stefan.

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