Question about project quota with container

[Christoph Hellwig]

> I was wondering if other file system will also implement project quota
> based on these two configuration files in the future? In other words, is
> it a standard?

The have been a few attempts at roughly similar quotas for ext4, but
they were incompatible enough to not reuse any infrastructure like this.

> 
> Alternatively, maybe the project path and ID can be setup at cgroup
> control files too, the following things could be implemented like
> "xfsprogs/quota/edit.c", but I would put aside this idea for now.

Assigning the project IDs in the cgroups code sounds fine to me.  To
make peoples life's easier it might be good idea to keep the
/etc/projects and /etc/projid files uptodate even from that code.