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Date: Sun, 23 Apr 1995 19:38:14 -0400
From: Thomas David Rivers <ponds!rivers@dg-rtp.dg.com>
Message-Id: <199504232338.TAA00879@lakes>
To: ref.tfs.com!julian@dg-rtp.dg.com, ponds!rivers
Subject: Re: Interesting SCSI cdrom problem..
Cc: freebsd-hackers@freefall.cdrom.com
Sender: hackers-owner@FreeBSD.org
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> 
> > 
> This is a 'feature' of the driver
> once the door has been openned, the drive reports to the driver, that
> there has been user intervention of some kind..
> specifically a 'Unit attention' erro is reported to the driver..
> 
> this tells the driver that the cdrom MAY HAVE BEEN CHANGED!.
> 
> The driver therefore aborts ALL operations until ALL USERS have closed the
> device. (including the 'mount' 'user' ).
> 
> When the last user has closed the device, operations on the cdrom are 
> re-enabled..
> 
> I'm glad to see you are getting this as it proves that the code in
> question is working, and it is vitally important to devices
> with read-write removable media that it does....
> consider..
> async write to drive...
> {change media}
> sync
>  (OUCH!)
> 
> the same problem exists for cdoms but it doesn't corrupt the media,
> just totally screws the internal cached copy of the filesystem nodes
> (i.e if it assumed that the same cdrom was in but wasn't.....)
> 

 Yes, that entirely makes sense.  I was considering the situation myself;
what else could you do given that the "disk" can be jerked out from under
you? 

	- Thanks -
	- Dave Rivers -