Comment 2 for bug 1595394

Hello Sergei,

We must acquire the checkpoint lock for the whole time of copying tokudb files, the purpose is to get a snapshot(in last checkpoint state) for all files(logs and data files).
The effects(only) we take checkpoint lock is that more and more redo-logs until the copying end.
This method has been used in our production(mysql-5.6+xtrabackup 2.2) for a long time, it works very well.