XFS reflink and development tip git trees updated

["Darrick J. Wong" <darrick.wong@oracle.com>]

Ok, here's this week's for-4.9 branch:

https://github.com/djwong/linux/tree/for-dave-for-4.9-5
https://github.com/djwong/xfsprogs/tree/for-dave-for-4.9-5

The kernel tree includes Christoph's fixes for copy-on-write,
refactoring of a refcount btree function to use _btree_query_range (and
inclusion of the required diff_two_keys/init_high_key helpers), and
removal of the (totally broken) always_cow debug switch.  It also
contains a new error injection point to make reflink fail with ENOSPC.

The xfsprogs tree incorporates the libxfs changes in the kernel tree
but is largely the same as last week's for-4.9-2 branch.  The only
change in userspace programs is that xfs_io can trigger the
above-mentioned error injection point.

---

The WTF trees have been rebased to 4.8-rc8 and xfsprogs for-next:
https://github.com/djwong/linux/tree/djwong-wtf
https://github.com/djwong/xfsprogs/tree/djwong-wtf

These two trees contain all the changes noted above as well as in-kernel
scrubbing of directory and extended attribute data.  xfs_scrub has been
modified to take advantage of them, and can now fall back a little more
gracefully when kernel scrubbing is unavailable.

(Note that the WTF tree doesn't reflect the iomap rework that's in the
4.9 for-next tree; I'll rebase WTF against 4.9 after the merge window
closes.  Unfortunately that's the only way to pick up scrub or realtime
rmap support.)

--D