On Mon, Aug 23, 2021 at 04:14:45PM -0400, Josef Bacik wrote:

In order to reduce the amount of pain the reviewers have to endure I'm going to
be sending any prepatory patches separately from the actual feature work.

To that end this is the first batch of preparatory patches.  These are to make
working with mkfs a lot easier for the changes I'm making.  These are all fixes
or enhancements that can apply currently.  The only thing that is extent tree v2
specific is the last patch, which adds the incompat flag.

I've added the patch for the incompat flag because I will have other preparatory
patches that add helpers that essentially do

if (!btrfs_fs_incompat(fs_info, EXTENT_TREE_V2))
	/* Do the old thing. */

and then have patches after that add the extent tree v2 magic.  I think this
will make it easier to break up the work, but if we're not comfortable reserving
the bit then I'm fine with dropping that last patch.  It will just mean future
prep work will have to come along with the feature enablement patches.

Going through the patches I don't think mentioning the extent tree v2
makes sense in case the patch is an independent cleanup or refactors
some code to be a bit more generic.

The actual incompat bit could be reserved but it would be better to keep
it in the future patchset implementing some significant part of the
extent tree v2.

Even with the "if (EXTENT_TREE_V2)" in place it becomes the
implementation and given that I haven't read the whole design doc for
that I'm worried that once I find time for that and would suggest some
changes the reply would be "no I did it this way, it's implemented,
would require too many changes".

Would be good to keep mentioning the v2 tree maybe to the cover letter
so we know what's the motivation but in the changelogs it's confusing as
we don't have any base point for that.