losetup from 7.6.1 can't detach a cloop device

[hb <hb09@mnet-mail.de>]

In this example cx.iso was created with genisoimage and create_compressed_fs

# ls -l cx.iso
-rw-r--r-- 1 root root 122052675 Jun  4 00:39 cx.iso
#
# losetup -V
losetup from util-linux 2.27.1
#
# losetup -r /dev/cloop7 cx.iso
losetup: cx.iso: Warning: file does not fit into a 512-byte sector; the
end of the file will be ignored.
# losetup -d /dev/cloop7
losetup: /dev/cloop7: failed to use device: Success
#

... and cloop7 is still attached.

The warning doesn't seem to be related to the failure, but what do I know.

A workaround is to use an older losetup, for example a local copy of the
one from 7.4.2:

# ./losetup -V
./losetup: invalid option -- 'V'

Usage:
 losetup loop_device                             give info
 losetup -a | --all                              list all used
 losetup -d | --detach <loopdev> [<loopdev> ...] delete
...
#
# ./losetup -r /dev/cloop7 cx.iso
# ./losetup -d /dev/cloop7
#

I didn't spend the time to look at the sources of losetup, I hope
someone with more knowledge about cloop will do.