When specifying a source='/some_file' it would be conveniant for cryptfs to find a free loop devices, bind the file to it and then call cryptsetup with that device. This would allow users to setup crypted filesystems inside files in an automated fashion. Reproducible: Always Steps to Reproduce: 1. 2. 3.
After looking at the recent comments in the file there is the loop_file option, but is there a way for cryptfs to automatically find and use the next free loop device?
currently not there is not, it would need to be specified. There is nothing stopping you from what you have originally stated doing, as you can set it up by specifying each mount that you want to do. I would accept patches for this, but right now I'm going to close this as won't fix as I don't see a compelling need for this feature as the functionality is there.
