btrfs: temporarily export fragment_free_space

This is used in caching and reading block groups, so export it while we
move these chunks independently.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2 files changed