Ceph » rbd

While attempting to test http://tracker.ceph.com/issues/3094
I learned that nothing prevented me from mapping the same
rbd image multiple times with write permission (on the same
node).

Mapping it for write from multiple nodes can only be prevented
using something like osd based locking. And that would be
sufficient here too, but the kernel and/or the rbd command
line utility could do more to prevent someone from mapping
the same image for writing more than once. Or perhaps allow
it, but require a "--force" flag or something to be successful.

(Mapping a writable image read-only is an available option,
even though that's risky in the presence of any mappings
that can be written.)