Problem mounting encrypted blu-ray disc or image

["B.M." <b-misc@gmx.ch>]

Hello

I create encrypted backups on blu-ray discs for some years now with a bash
script, but now I encountered a problem mounting some of these discs (but not
all of them - in fact, my last backups consist of two discs each, and I cannot
mount the first one but I can mount the second one for each of them - seems
strange...). It's not date-related (and they are not too old).

In detail, I use the following commands:

IMGFILE=/home/TMP_BKP/backup.img
IMGSIZE=24064000K
IMGLOOP=`losetup -f`

touch $IMGFILE
truncate -s $IMGSIZE $IMGFILE
losetup $IMGLOOP $IMGFILE
cryptsetup luksFormat --cipher aes-xts-plain64 $IMGLOOP
cryptsetup luksOpen $IMGLOOP BDbackup
mkudffs -b 2048 --label $1 /dev/mapper/BDbackup
mount -t udf /dev/mapper/BDbackup /mnt/BDbackup

... then I create my compressed backup files ...

umount /mnt/BDbackup
cryptsetup luksClose /dev/mapper/BDbackup
losetup -d $IMGLOOP

growisofs -dvd-compat -Z /dev/dvd=$IMGFILE; eject


In order to mount the disc, I use:

cryptsetup luksOpen -r /dev/dvd BDbackup
mount -t udf /dev/mapper/BDbackup /mnt/BDbackup


Unfortunately, this fails now for some of my discs and also for the last image
file I created (not deleted yet...):

mount: /mnt/BDbackup: wrong fs type, bad option, bad superblock on /dev/
mapper/BDbackup, missing codepage or helper program, or other error.

And dmesg shows:

UDF-fs: warning (device dm-10): udf_load_vrs: No VRS found
UDF-fs: Scanning with blocksize 2048 failed
UDF-fs: warning (device dm-10): udf_load_vrs: No VRS found
UDF-fs: Scanning with blocksize 4096 failed


Any ideas what may happen here?

Thank you.

Best,
Bernd