[RFC PATCH 0/10] relay revamp, third installment

[Tom Zanussi <zanussi@comcast.net>]

Here's the current relay cleanup patchset.

1-2 make the write path completely replaceable.
3 adds flags along with some related cleanup.
4-8 remove the padding in several stages.

The new patches in this set are:

9 simplifies the callbacks - now that we have flags, the subbuf_start
callback is much simpler, has been combined with notify_consumers and
has been renamed new_subbuf.  Because part of the simplification has
been to handle buffer-full conditions and count lost events internally,
normal applications don't have to pay attention to it at all.

10 completely removes the idea of sub-buffers completely and now deals
only with pages. relay_open() channges accordingly - buffer sizes are
now in pages and consumers are woken only every n_wakeup pages, or never
if this is 0. 

It's a work in progress, but because I wanted the intermediate stages to
actually work and not break anything, some of these patches, especially
05, are just temporary and will be removed in the next iteration.

I didn't have time to clean up the first 3 either - I'll also do that
the next time around.

In the next round I plan to do vmap removal.

Tom