Open Stack

This may mostly be a Cinder concern, but putting it out there to get
wider input.

For some time now there has been some debate about moving third party
drivers in Cinder to be out of tree. I won't go into that too much,
other than to point out one of the major drivers for this desire that
was brought up at our recent Cinder midcycle.

It turned out at least part of the desire to move drivers out of tree
came down to the difficulty in getting bug fixes out to end users that
were on older stable versions, whether because that's what their distro
was still using, or because of some other internal constraint that
prevented them from upgrading.

A lot of times what several vendors ended up doing is forking Cinder to
their own github repo and keeping that in sync with backports, plus
including driver fixes they needed to get out to their end users. This
has a few drawbacks:

1- this is more work for the vendor to keep this fork up to date
2- end users don't necessarily know where to go to find these without
   calling in to a support desk (that then troubleshoots a known issue
   and hopefully eventually ends up contacting the folks internally that
   actually work on Cinder that know it's been fixed and where to get
   the updates). Generally a bad taste for someone using Cinder and
   OpenStack.
3- Distros that package stable branches aren't able to pick up these
   changes, even if they are picking up stable branch updates for
   security fixes
4- We end up with a lot of patches proposed against security only stable
   branches that we need to either leave or abandon, just so a vendor
   can point end users to the patch to be able to grab the code changes

Proposed Solution
-----------------

So part of our discussion at the midcycle was a desire to open up stable
restrictions for getting these driver bugfixes backported. At the time,
we had discussed having new branches created off of the stable branches
specifically for driver bugfixes. Something like:

stable/mitaka > stable/mitaka-drivers

After talking to the infra team, this really did sound like overkill.
The suggestion was to just change our stable policy in regards to driver
bugfix backports. No need to create and maintain more branches. No need
to set up gate jobs and things like that.

So this is a divergence from our official policy. I want to propose
we officially make a change to our stable policy to call out that
drivers bugfixes (NOT new driver features) be allowed at any time.

If that's not OK with other project teams that support any kind of third
party drivers, I will just implement this policy specific to Cinder
unless there is a very strong objection, with good logic behind it, why
this should not be allowed.

This would address a lot of the concerns at least within Cinder and
allow us to better support users stuck on older releases.

I'm open and welcome to any feedback on this. Unless there are any major
concerns raised, I will at least instruct any Cinder stable cores to
start allowing these bugfix patches through past the security only
phase.

Thanks!

Sean McGinnis (smcginnis)