Merge branch 'idr-4.11' of git://git.infradead.org/users/willy/linux-dax

Pull IDR rewrite from Matthew Wilcox:
 "The most significant part of the following is the patch to rewrite the
  IDR & IDA to be clients of the radix tree. But there's much more,
  including an enhancement of the IDA to be significantly more space
  efficient, an IDR & IDA test suite, some improvements to the IDR API
  (and driver changes to take advantage of those improvements), several
  improvements to the radix tree test suite and RCU annotations.

  The IDR & IDA rewrite had a good spin in linux-next and Andrew's tree
  for most of the last cycle. Coupled with the IDR test suite, I feel
  pretty confident that any remaining bugs are quite hard to hit. 0-day
  did a great job of watching my git tree and pointing out problems; as
  it hit them, I added new test-cases to be sure not to be caught the
  same way twice"

Willy goes on to expand a bit on the IDR rewrite rationale:
 "The radix tree and the IDR use very similar data stru...