On Fri, 2017-02-17 at 14:57 +1300, Eric W. Biederman wrote: > I think I am missing something but I completely do not understand > that subthread that says use file marks and perform the work in the > vfs. The problem is that fundamentally we need multiple mappings and > I don't see a mark on a file (even an inherited mark) providing the > mapping so I don't see the point. The point of the mark is that it's a statement by the system administrator that the underlying subtree is safe to be mounted by an unprivileged container in the containers user view (i.e. with current_user_ns() == s_user_ns). For the unprivileged container there's no real arbitrary s_user_ns use case because the unprivileged container must prove it can set up the mapping, so it would likely always be mounting from within a user_ns with the mapping it wanted. James
