Union mounts (writable overlays) documentation and release

I just posted the union mounts (now called writable overlays) design doc to LKML and fsdevel:

[RFC] Union mounts/writable overlays design

Along with it is a new release, featuring:

* Rebase against 2.6.31
* pivot_root() and rename() support
* jffs2 support (thanks to Felix Fietkau)

I booted this one on my laptop with a root file system as a writable overlay, and got all the way up to the (text) login prompt with only a couple of complaints about missing chmod() and link() support. Yeah!

The patches that need to be rewritten have useful comments in their commit messages, and the fixes are described in detail in the design doc. So if you want to jump in and do a little bit of development, you can do so even if you’re not a VFS expert (which is most of us).

As usual, all the good stuff linked to from here:

Writable overlays (a.k.a. union mounts)

Have fun!