[6189] in linux-scsi channel archive
Re: CD does not allow concurrent access
daemon@ATHENA.MIT.EDU (Gadi Oxman)
Fri Mar 26 06:23:44 1999
Date: Fri, 26 Mar 1999 12:45:31 +0300 (IDT)
From: Gadi Oxman <gadio@netvision.net.il>
To: Kurt Garloff <K.Garloff@ping.de>
cc: Linux SCSI list <linux-scsi@vger.rutgers.edu>
In-Reply-To: <19990326083051.C6565@kg1.ping.de>
On Fri, 26 Mar 1999, Kurt Garloff wrote:
> Hi there,
>
> is the following a known problem?
>
> For copying a CD, I made an image by just using
> cat /dev/sr0 >cd.img
>
> In the meantime, I wanted to inspect the CD. Mounting and accessing the CD
> caused the cat command to abort with I/O error. Doing the cat again without
> any concurrent access to the CD, it worked.
> Concurrent access to other devices on the SCSI bus does not harm.
>
> This is bad behaviour IMHO.
>
> Details: Linux-2.2.2-ac7, SMP, ncr53c8xx (Tekram DC390F), Plextor Px32Ts
> More details on request.
>
> --
> Dipl.Phys. Kurt Garloff <kurt@garloff.de> [Dortmund, FRG]
> Plasma physics, high perf. computing [Linux-ix86,-axp, DUX]
> PGP key: see mailheader / key servers [Linux SCSI driver: DC390]
My guess is that this us due to the block size being changed during
operation; by default, cat /dev/sr0 > cd.img is probably using a block
size of 2048. When you mounted the media, the block size was being
changed from under the cat operation to 1024, and multiple block
sizes are not being supported concurrently.
I believe that after one mount, doing additional cat commands will use
the 1024 bytes block size and will no longer abort with I/O error.
Alternatively, reloading the cdrom driver, and mounting the cdrom
with the -o bs=2048 argument should also not fail the cat command, as
the block size will not be changed.
Gadi
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