seems that it is trying to call mount.zfs... see attached log Reproducible: Always
Created attachment 419414 [details] rdsosreport.txt
https://gist.github.com/1321ac579366bc153362 has a working patch, but it's not my code (it's rudd-o's). https://github.com/zfsonlinux/zfs/issues/3605
looks like it's fixed upstream. closing.