[PATCH 0/3][v2] Add comments describing how space reservation works

[Josef Bacik <josef@toxicpanda.com>]

v1->v2:
- Fixed spelling mistakes, discovered you can use ':set spell' for files other
  than git commit messages.
- Reworked some of the explanations to be more visual to describe the general
  flow.

--------------- Original email ------------------
In talking with Nikolay about the data reservation patches it became clear that
there's way more about the space reservation system that exists soley in my head
than I thought.  I've written three big comments on the different sections of
the space reservation system to hopefully help people understand how the system
works generally.  Again this is from my point of view, and since I'm the one who
wrote it I'm not sure where the gaps in peoples understanding is, so if there's
something that is not clear here now is the time to bring it up.  Hopefully this
will make reviewing patches I submit to this system less scary for reviewers.
Thanks,

Josef