This reuses the existing code for checking the free space cache, we just
need to load the free space tree. While we do that, we check a couple of
invariants on the free space tree itself. This requires pulling in some
code from the kernel to exclude the super stripes.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
