dm-3.16-changes

. Add dm_accept_partial_bio interface to DM core to allow DM targets
  to only process a portion of a bio, the remainder being sent in the
  next bio.  This enables the old dm snapshot-origin target to only
  split write bios on chunk boundaries, read bios are now sent to the
  origin device unchanged.

. Add DM core support for disabling WRITE SAME if the underlying SCSI
  layer disables it due to command failure.

. Reduce lock contention in DM's bio-prison.

. A few small cleanups and fixes to dm-thin and dm-era.
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