CLUSTER_TO_BITMAP_ENT
ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
ent_idx = ALIGN_DOWN(CLUSTER_TO_BITMAP_ENT(clu), BITS_PER_LONG);
ent_idx = CLUSTER_TO_BITMAP_ENT(start);
BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu));
BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu+1));
BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(n_clu));