bcachefs: Track incompressible data

This fixes the background_compression option: wihout some way of marking
data as incompressible, rebalance will keep rewriting incompressible
data over and over.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
11 files changed