On Sun, Aug 10, 2014 at 01:47:24PM -0700, James Bottomley wrote:

Actually, I don't believe that's entirely accurate.  The performance
problem with shared filesystem roots for containers has meant OpenVZ has
been using a block root for a while.  However, we still support the old
shared filesystem root, but for quota's within the chroot, we use a subtree
quota system (not a project quota) for which Dmitry Monakhov
posted the patches several times a couple of years ago.

The XFS-compatible project quota is effectively a subtree quota
system.  My argument is that if we're going to try to get something
like this upstream, it should have the same properties as the XFS
project quota system; and that should be semantically compatible with
the patches you are using.

(If we end up using the same ioctl's as xfs_quota uses, which in
theory I'm in favor of, but which I haven't studied yet, then it might
not be ABI compatible with Dmitry's patches, but it should simplify
the patches that OpenVZ would need to carry.)

					- Ted