Thanks for comments.
But that said, I find the log spam today from e.g. docker + devicemapper + xfs annoying, and switching to overlay2 fixed that as a side effect which is nice. Having overlay2 log would reintroduce that problem.
You are right, docker with overlay2 logs additional 6 lines during container run. Though originally I was thinking overlay logs are important, now I have to log only FS of type FS_REQUIRES_DEV. With this its just two lines, during docker run.
Added this to v2. Thanks, Anand
