[$] Container-aware filesystems
We are getting closer to being able to do unprivileged mounts inside
containers, but there are still some pieces that do not work well in that
scenario. In particular, the user IDs (and group IDs) that are embedded
into filesystem images are problematic for this use case. James Bottomley
led a discussion on the problem in a session at the 2017 Linux Storage,
Filesystem, and Memory-Management Summit.