kern/39808: can't unmount CD with media error

[M.Drochner%fz-juelich.de@localhost]

>Number:         39808
>Category:       kern
>Synopsis:       can't unmount CD with media error
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Oct 26 10:10:01 +0000 2008
>Originator:     Matthias Drochner
>Release:        -current (from ~2 weeks ago)
>Organization:
>Environment:
NetBSD zelz27 4.99.73 NetBSD 4.99.73 (MIST+MP) #194: Wed Oct 15 16:32:08 MEST 
2008  
drochner@zelz27:/home/drochner/netbsd/work.src.usbdev/sys/arch/i386/compile/MIST+MP
 i386
>Description:
I could mount an iso9660 file system from a CD.
Any access to the data failed. Appearently the CD is damaged.
That happens... but I wasn't able to unmount it:

# mount /dev/cd0a /mnt
# $ ls -l /mnt
ls: /mnt: Input/output error
$ su
[...]
# umount /mnt
umount: /mnt: Input/output error
# umount -f /mnt
umount: /mnt: Input/output error
# dmesg
[...]
cd0(piixide0:1:0):  Check Condition on CDB: 0x28 00 00 00 00 1c 00 00 01 00
    SENSE KEY:  Media Error
     ASC/ASCQ:  L-EC Uncorrectable Error

>How-To-Repeat:
See above. Might be hard to get that specific read error from a CD.
Would be good to have some way of error injection in the disk drivers.

>Fix: