I'm attempting to create the mapper device in the initrd however I'm experiencing an odd issue. When running the flashcache_create command it fails although if I manually run the output (echo ... ... | dmsetup). It runs fine and works as expected.
I'm not sure if this is a bug with the flashcache_create utility or in my environment.
I was able to achieve this by using dmsetup directly - I'm unsure as to why flashcache_create wasn't working.