On Fri, 26 Feb 2016 22:00:44 +0100, Stanislav Brabec said:

> Well, it seems to be safe, even if the loop device was not allocated by 
> mount(8) itself, as
> ioctl(fd, LOOP_CLR_FD)
> never returns EBUSY:

The fact you don't get an EBUSY doesn't mean it's actually safe....