nilfs_segment_usage_clean
if (!nilfs_segment_usage_clean(su))
if (!nilfs_segment_usage_clean(su))
if (unlikely(!nilfs_segment_usage_clean(su))) {
clean = nilfs_segment_usage_clean(su);
if (nilfs_segment_usage_clean(su)) {
suclean = nilfs_segment_usage_clean(su);
cleansu = nilfs_segment_usage_clean(su);