dm bio prison: introduce support for locking ranges of blocks

Ranges will be placed in the same cell if they overlap.

Range locking is a prerequisite for more efficient multi-block discard
support in both the cache and thin-provisioning targets.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --cc drivers/md/dm-bio-prison.c
Simple merge

diff --cc drivers/md/dm-bio-prison.h
Simple merge

diff --cc drivers/md/dm-cache-target.c
Simple merge

diff --cc drivers/md/dm-thin.c
Simple merge