bin/54163: Unable to mount IRIX install cdroms with mount_efs(8)

[venture37%geeklan.co.uk@localhost]

>Number:         54163
>Category:       bin
>Synopsis:       Unable to mount IRIX install cdroms with mount_efs(8)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun May 05 18:55:00 +0000 2019
>Originator:     Sevan Janiyan
>Release:        NetBSD-HEAD
>Organization:
>Environment:
NetBSD 8.99.37 amd64 x86_64
>Description:
Attempting to mount a cd always returns "Invalid argument"

# mount_efs /dev/cd0a  /mnt               
mount_efs: /dev/cd0a on /mnt: Invalid argument

# mount_efs /dev/cd0d  /mnt 
mount_efs: /dev/cd0d on /mnt: Invalid argument

# mount_efs /dev/cd0  /mnt  
mount_efs: /dev/cd0 on /mnt: Invalid argument


# disklabel cd0                                                                             
# /dev/rcd0:
type: ATAPI
disk: optical media
label: fictitious
flags: removable
bytes/sector: 2048
sectors/track: 100
tracks/cylinder: 1
sectors/cylinder: 100
cylinders: 2805
total sectors: 280536
rpm: 300
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0		# microseconds
track-to-track seek: 0	# microseconds
drivedata: 0 

4 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:    280536         0     4.2BSD      0     0     0  # (Cyl.      0 -   2805*)
 d:    280536         0        UDF                     # (Cyl.      0 -   2805*)
disklabel: boot block size 0
disklabel: super block size 0
disklabel: partitions a and d overlap


# mount /dev/cd0a /mnt                                                                      
mount_ffs: /dev/cd0a on /mnt: incorrect super block

# mount_udf  /dev/cd0d /mnt                                                                 
mount_udf: Cannot mount /dev/cd0d on /mnt: Read-only file system

# mount_udf -o rdonly /dev/cd0d /mnt
mount_udf: Cannot mount /dev/cd0d on /mnt: Invalid argument
>How-To-Repeat:
Insert IRIX install in CD/DVD drive and try to mount with mount_efs

I'm using physical media but images are available here: https://archive.org/details/sgi_IRIX_6.5_Foundation_1
>Fix: