On Tue, Feb 07, 2017 at 11:49:33AM -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.
I'm interested in having a VFS-level way to do more than just a shift; I'd like to be able to arbitrarily remap IDs between what's on disk and the system IDs. If we're talking about developing a VFS-level solution for this, I'd like to avoid limiting it to just a shift. (A shift/range would definitely be the simplest solution for many common container cases, but not all.)
