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Date:      Mon, 28 Sep 1998 02:32:44 +0100 (MET)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        tlambert@primenet.com (Terry Lambert)
Cc:        wollman@khavrinen.lcs.mit.edu, dan@math.berkeley.edu, sos@FreeBSD.ORG, current@FreeBSD.ORG
Subject:   Re: cd9660 mounts...
Message-ID:  <199809280132.CAA02773@labinfo.iet.unipi.it>
In-Reply-To: <199809272133.OAA00234@usr05.primenet.com> from "Terry Lambert" at Sep 27, 98 09:32:52 pm

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> > 	mount -t cd9660 -o track=-1 /dev/cd0c /cdrom
> > 
> > ..which would cause it to find the last track with an ISO-9660
> > filesystem on it, and mount that.  (The current behavior is totally
> > broken for PhotoCD, since there are normally garbage tracks after the
> > one which contains the real data, so I always have to use ``cdcontrol
> > info'' and do the scanning manually.)
> 
> FWIW, this is supposed to be the default behaviour for a multisession
> CD, according to the Joliet spec. (go to the last session with a
> CD9660 FS, and mount it).

our code does something like that now, but my feeling is that is is
broken. Essentially the problem is: when a track is not at offset 0 who
is in charge of adding the offset for the track to all reads ?

* If you do it in the driver as i did, it is only one place to modify.

* if you do it in the cd9660 fs code, i think you have to trap all
  code paths which end up in doing a bread(). I tried this but probably
  failed to find all of them.

* there is a possibility (I don't have the cd9660 specs) that in a
  multisession CD, the data track is created knowing exactly where it
  is going to go on a disk (and what is on the previous tracks) so
  the track image already contains the correct block addresses and no
  offset needs to be added.

The FreeBSD cd9660/mount_cd9660 _might_ work in the latter case, but i
don't have a multisession CD to try and I want to remark that mkisofs
has no flags/options to create this kind of tracks.

	cheers
	luigi


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