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[RFC] Handling of reviewed patch series

To: xfs@xxxxxxxxxxx
Subject: [RFC] Handling of reviewed patch series
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 13 Dec 2013 16:36:11 +1100
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mutt/1.5.21 (2010-09-15)
Hi folks,

I'd like to make a proposal and see what people think abou tit for
managing patch series that I have been reviewed.

What I'd like to do is publish the reviewed and signed-off topic
branches that I built as in my local git tree as part of the review
and test process. For example, I currently have two such branches
right now - one for Christoph's log format changes, and another for
Jeff's icluster cleanups.

That is:

$ git shortlog xfs-oss/master..guilt/tip-log-format
Christoph Hellwig (10):
      xfs: remove duplicate code in xlog_cil_insert_format_items
      xfs: refactor xfs_buf_item_format_segment
      xfs: refactor xfs_inode_item_size
      xfs: refactor xfs_inode_item_format
      xfs: introduce xlog_copy_iovec
      xfs: format log items write directly into the linear CIL buffer
      xfs: format logged extents directly into the CIL
      xfs: remove the inode log format from the inode log item
      xfs: remove the dquot log format from the dquot log item
      xfs: remove the quotaoff log format from the quotaoff log item

$ git shortlog xfs-oss/master..guilt/tip-icluster-factor 
Jie Liu (8):
      xfs: get rid of XFS_IALLOC_INODES macros
      xfs: get rid of XFS_INODE_CLUSTER_SIZE macros
      xfs: get rid of XFS_IALLOC_BLOCKS macros
      xfs: introduce a common helper xfs_icluster_size_fsb
      xfs: use xfs_icluster_size_fsb in xfs_bulkstat
      xfs: use xfs_icluster_size_fsb in xfs_ialloc_inode_init
      xfs: use xfs_icluster_size_fsb in xfs_ifree_cluster
      xfs: use xfs_icluster_size_fsb in xfs_imap

These branches are all based on the master branch as it currently
stands. They have had each patch individually compile tested, they
have been individually tested, and they've been merged into a test
tree and tested along with every other branch I'm currently working
on.

What I'd like to do is publish each of the reviewed branch in the
XFS git repos on oss.sgi.com as completed and ready-to-go code. This
is a bit different to what we do now - normally Ben would come along
and merge the series straight into the master branch, then update
the for-next branch to point at it.

The issue with this is that it then makes our lives more difficult
when we get a bug fix that has to go into the master branch and be
sent to linus for an -rc kernel before all the development code that
is already checked into the master branch.

What I propose is that the xfs-oss/master branch tracks the Linus
-rc1 releases, and we never check code directly into the master
branch except in exceptional circumstances. i.e.  we try to only
ever pull back down from Linus into it. Exceptional circumstances
would be work that causes widespread rebasing, like all of the
structural rework that we've done recently. The structural work
would go into the master branch immediately after a -rc1 update, and
the next cycle's work and topic branches then based on top of that.

What this means is that the "for-next" branch is no longer based
on the master branch - it becomes the development branch we work on,
and is effectively a merge of all the topic branches. i.e like the
-next tree, it is a branch that can be rebased without impacting the
history of the code in the topic branches because it's just a merge
target.

What this means is that development can be done against the master
branch without fear of conflicting with other changes that are being
done. Testing, however, can target the for-next branch, and local
integration testing can be done simply by merging a local topic
branch into a local for-next branch....

Lines of development that overlap will generate conflicts at
the for-next branch merge, and at that point we can decide how to
deal with the problem. e.g. turn the conflicting topic branches into
a single, larger topic branch, live with it, etc.

When it comes to sending code upstream to Linus, we can either send
a pull request per topic branch - Linus often likes to do merges
himself - or we can merge them all into a single branch and ask
Linus to pull that. The deciding factor may well be Linus himself...

However, what this structure means is that urgent bugs fixes canbe
placed into their own topic branches - an "urgent-*" prefix is often
used for these by other maintainers - and Linus can pull directly
from the topic branch without us having to worry about
cherry-picking out of the middle of the master branch and all the
pain that entails.

It also allows us much more flexibility in managing the
code and how it is send upstream. It also makes it possible to push
code earlier for wider testing without being stuck with that code
forever - it's trivial to drop a topic branch if it causes
unexpected regressions or problems without leaving nasty reverts all
over the history.

Yes, this is a bit of a change in the way we do things, but it
aligns much more closely to the distributed nature of how we develop
the code. I'm going to push the two topic branches I mentioned above
into the oss repository so people can have a look at them and get a
feel for how such a process might work and so we can reference them
during the discussion.

Essentially, I want to speed up the rate at which we get code
integrated without the risk of making a big mess by committing to
code too quickly. Keeping code in topic branches like this solves
that problem, and the fact that it closely aligns to my normal
workflow makes it very appealing to me as a Maintainer....

Keep in mind that I want to do the same thing for major pieces of
work with xfstests and xfsprogs - keep work in topic branches until
they are tested and ready to go, then merge everything into the master
branch and cut a release. This would enable a much faster xfsprogs
release schedule because we make a release at any point in time
without having to worry about whether we have work in progress in
the master branch that needs completing before a release is done...

Anyway, have a think and discuss - I'm going to push the branches I
mentioned above....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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