ocfs2_dir_trailer_blk_off
#define ocfs2_trailer_from_bh(_bh, _sb) ((struct ocfs2_dir_block_trailer *) ((_bh)->b_data + ocfs2_dir_trailer_blk_off((_sb))))
size = ocfs2_dir_trailer_blk_off(sb);
offset, ocfs2_dir_trailer_blk_off(dir->i_sb));
size = ocfs2_dir_trailer_blk_off(parent->i_sb);
new_size = ocfs2_dir_trailer_blk_off(sb);
de->rec_len = cpu_to_le16(ocfs2_dir_trailer_blk_off(sb));
free_space = ocfs2_dir_trailer_blk_off(sb) - i_size_read(dir);