Merge tag 'for-4.18/dm-changes-v2' of git://git.kernel.org/pub/scm/linux/kernel/git...

Pull device mapper updates from Mike Snitzer:

 - Adjust various DM structure members to improve alignment relative to
   4.18 block's mempool_t and bioset changes.

 - Add DM writecache target that offers writeback caching to persistent
   memory or SSD.

 - Small DM core error message change to give context for why a DM table
   type transition wasn't allowed.

* tag 'for-4.18/dm-changes-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm: add writecache target
  dm: adjust structure members to improve alignment
  dm: report which conflicting type caused error during table_load()