I should be able to specify the default for a filesystem as a
mount option, then set an attribute to include/exclude directories
as I choose. Perhaps I have one partition for the whole system,
and I want it to be fast. I want atime to work for /var/spool/mail.
I want to let users turn on atime for their own directories and files,
but it should be disabled by default. I want to enable atime in /tmp,
but then users should be able to turn it off.
Looks like it needs to be a bit that can be turned on and off,
and which is inherited from the parent directory. If chattr
affects the mounted filesystem at a mount point, then an attribute
alone should be good enough.