Comment 5 for bug 1049582

I can't really reproduced, don't have a similar setup ready. However, analyzing the backtrace and the code, the following may fix the issue:
https://github.com/ceph/ceph/commit/2fddfb0a95288d39cee2e82376297ce43296743b

It has already been pushed to the ceph stable branch, though it's not in any tagged version yet.