dm cache policy: add/refine DMWARN messages in dm_cache_policy_register
dm cache policy: refactor get_policy to use IS_ERR
[dm-cache] update documentation
[dm-cache] make constructor comment match cache.txt (formatting)
dm cache metadata: set policy_hint_size in dm_cache_metadata_open
Merge branch 'thin-dev' of git://github.com/snitm/linux into cache-review-work2
[dm-cache] add some DM_ prefixes to #defines
[dm-cache] I see no need to pass the set_config through to the policy.
[dm-cache] tidy dm_cache_init
[dm-cache] fluff
Merge branch 'thin-dev' into all-caches