This is currently an RFC because the patch applies to Linus head, but needs altering for the vfs tree, so I'll respin and resend after the merge window closes. My use case for this is that I run a lot of unprivileged architectural emulation containers on my system using user namespaces. Details here: http://blog.hansenpartnership.com/unprivileged-build-cont... They're mostly for building non-x86 s