On Tue, 2017-02-07 at 11:49 -0800, Christoph Hellwig wrote: > On Tue, Feb 07, 2017 at 11:02:03AM -0800, James Bottomley wrote: > > > Another option would be to require something like a project as > > > used > > > for project quotas as the root. This would also be conveniant as > > > it > > > could storge the used remapping tables. > > > > So this would be like the current project quota except set on a > > subtree? I could see it being done that way but I don't see what > > advantage it has over using flags in the subtree itself (the > > mapping is > > known based on the mount namespace, so there's really only a single > > bit > > of information to store). > > projects (which are the underling concept for project quotas) are > per-subtree in practice - the flag is set on an inode and then > all directories and files underneath inherit the project ID, > hardlinking outside a project is prohinited. OK, this is what I don't understand: how is something that's inode based limited to be per-subtree? The way I've seen the VFS operate it seems that any given inode (and indeed dentry) can appear in many subtrees so how do I limit them to just one? James
