dm-crypt: support relaxed memory alignment

From: Keith Busch <kbusch@kernel.org>

Resending as the previous send was bad timing with the merge window.

Direct-io can support any memory alignment the hardware allows. Device
mappers don't need to impose any software constraints on memory
alignment, so this series removes one of those limitations the dm-crypt
mapper.

Changes from v2:

 * Don't change the default stacking limit to allow the relaxed memory
   alignment requirements; have the caller do it instead.

 * Fixed scatterlist memory leaks when handling the case that can't
   use the inline scatterlist.

 * Fixed segment boundary check to use the crypt_config rather than the
   lower level block device's dma_alignment, which may not be the same
   size as the cc->sector_size which was used before, or the newly
   enabled 4-byte alignment this patch set allows in certain
   circumstances. 

Keith Busch (2):
  dm-crypt: allow unaligned bio_vecs for direct io
  dm-crypt: dynamic scatterlist for many segments

 drivers/md/dm-crypt.c | 114 ++++++++++++++++++++++++++++++++++--------
 drivers/md/dm-table.c |   1 +
 2 files changed, 94 insertions(+), 21 deletions(-)

-- 
2.47.3