Re: [RFC 1/1] shiftfs: uid/gid shifting bind mount

[Christoph Hellwig]

On Tue, Feb 07, 2017 at 07:59:00PM +0200, Amir Goldstein wrote:
> I am not even sure that would be enough.
> dentry does not contain information about the mount user came from,
> and sb contains only information about the user ns of the mounter of
> the file system, not the mounter of the bind mount, right?
> I think I am missing some big pieces of the big picture.
> Would love to hear what Eric has to say.

IFF we want to do what shiftfs does properly we need vfsmount + inode,
no need for the dentry.

But maybe we need to go back and decice if we want to allow uid/gid
remapping for arbitrary subtrees anyway.  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.