dm cache: add cleaner policy

A simple cache policy that writes back all data to the origin.

This is used to decommission a dm cache by emptying it.

Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index adc8710..7ceeaef 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -13,6 +13,7 @@
 dm-thin-pool-y	+= dm-thin.o dm-thin-metadata.o
 dm-cache-y	+= dm-cache-target.o dm-cache-metadata.o dm-cache-policy.o
 dm-cache-mq-y   += dm-cache-policy-mq.o
+dm-cache-cleaner-y += dm-cache-policy-cleaner.o
 md-mod-y	+= md.o bitmap.o
 raid456-y	+= raid5.o
 
@@ -48,6 +49,7 @@
 obj-$(CONFIG_DM_VERITY)		+= dm-verity.o
 obj-$(CONFIG_DM_CACHE)		+= dm-cache.o
 obj-$(CONFIG_DM_CACHE_MQ)	+= dm-cache-mq.o
+obj-$(CONFIG_DM_CACHE_CLEANER)	+= dm-cache-cleaner.o
 
 ifeq ($(CONFIG_DM_UEVENT),y)
 dm-mod-objs			+= dm-uevent.o