[dm-cache] remove some redundant includes
[dm-cache] factor struct cache_stats out of struct cache
[dm-cache] comment for prealloc_get/put_cell
[dm-cache] use sector_div where we can rather than do_div
[dm-cache] rename dm_cache_get/set_stats to dm_cache_metadata_get/set_stats
[dm-cache] update a warning
[dm-cache] Change a comment so it does not reference the current dev state of thinp
[dm-cache] remove some debug pr_alerts
[dm-cache] replace ensure_args with at_least_one_arg
[dm-cache] remove the parse macro
[dm-cache] rename _migration_cache to migration_cache
[dm-cache] BUG.  cache->features was being used before initialisation
[dm-cache] clarify the return code from process_config_option
[dm-cache] add comment for cache_message
[dm-cache] add missing __exit
[dm-cache] refactor get_policy to avoid a spin_unlock/lock sequence
[dm-cache] put_policy() should come after call to destroy
[dm-cache] fluff, avoid an else
[dm-cache] whitespace
[dm-cache] remove some dead code from cleaner