turn hmm migrate_vma upside down v3

[Jason Gunthorpe]

On Wed, Aug 14, 2019 at 09:59:18AM +0200, Christoph Hellwig wrote:
> Hi Jérôme, Ben and Jason,
> 
> below is a series against the hmm tree which starts revamping the
> migrate_vma functionality.  The prime idea is to export three slightly
> lower level functions and thus avoid the need for migrate_vma_ops
> callbacks.
> 
> Diffstat:
> 
>     7 files changed, 282 insertions(+), 614 deletions(-)

Yay, another big wack of code gone
 
Applied to hmm.git

Thanks,
Jason