hfs_bmap_get_map_page
page = hfs_bmap_get_map_page(node, &ctx, node_bit_idx / BITS_PER_BYTE);
page = hfs_bmap_get_map_page(node, &ctx, node_bit_idx / BITS_PER_BYTE);
page = hfs_bmap_get_map_page(node, &ctx, 0);
page = hfs_bmap_get_map_page(node, &ctx, 0);