Fix passthrough mode
dm-cache-target: use is_write_io() throughout
dm-cache-target: use cell_defer() boolean argument consistently
dm-cache-target: log error message if dm_kcopyd_copy() fails
dm-cache-target: use cache->quiescing boolean correctly
dm-cache-target: add missing from_cblock() cases
dm-cache-target: check commit_requested flag _before_ calling dm_cache_changed_this_transaction() superfluously
add policy_invalidate_mapping() API
dm-cache-policy-hints.c: fluff
dm-cache-shim-utils.c: use appropriate policy_*() inlines rather than calling methods directly
dm-cache-stack-utils.c: factor out __policy_destroy_stack() and fluff (empty lines for better legibility)
dm-cache-policy-{era,trc}+.c: support policy_invalidate_mapping(), use policy_*() inline functions, fix spinlock based era_counter increment
dm-cache-metadata.c: enforce modulo 4 cache hint size
dm-cache: allow for background and basic cache policies (Makefile,Kconfig)
dm-cache-policy-{era+,mq}.c: fix return code from era_invalidate_map() and remove superfluous mutex_lock() from mq policy
dm-cache-policy-era+.c: fix return check of __find_invalidate_block and types therin
[dm-cache] check the metadata version when we read the superblock
Merge remote-tracking branch 'remotes/github-heinz/cache-coherency-changes' into cache-coherency-changes
[dm-cache] remove some Kconfig entries