Comment # 9 on bug 1012504 from Stanislav Brabec

I just debugged the issue.

On the first sight it indeed looks like the issue mentioned in the comment 7.
But when checking deeper, it is a different issue. It is a problem of
util-linux mount.

Here is a simple reproducer:

#!/bin/sh
mkdir -p cdrom
mkisofs -o cdrom.iso cdrom/ 2>/dev/null
losetup /dev/loop0 cdrom.iso
strace mount -t auto -o ro,loop=/dev/loop1 cdrom.iso /mnt 2>&1 | grep ^mount
cat /proc/self/mountinfo | grep /mnt
umount /mnt
losetup -d /dev/loop0


mount("/dev/loop0", "/mnt", "iso9660", MS_MGC_VAL|MS_RDONLY, NULL) = 0
333 60 7:0 / /mnt ro,relatime shared:241 - iso9660 /dev/loop0 ro
losetup: /dev/loop0: detach failed: No such device or address

=> You called
mount -t auto -o ro,loop=/dev/loop1 cdrom.iso /mnt
                                  ^
but mount(8) called:
mount("/dev/loop0", "/mnt", "iso9660", MS_MGC_VAL|MS_RDONLY, NULL) = 0
                ^

It looks like a regression introduced by a patch set
util-linux-loop-reuse-*.patch: The reuse code must not be activated for
-oloop=/dev/loop1.


Note: I failed to reproduce the kernel corruption with iso9660. It's
reproduction vector probably depends on btrfs.