extent_ad
memset(&lvint->next_extent, 0, sizeof(struct extent_ad));
crclen = sizeof(struct unalloc_sp_desc) - sizeof(struct extent_ad);
elmsz = sizeof(struct extent_ad);
struct extent_ad main_vds_ex; /* to main volume descriptor set ; 16 sectors min */
struct extent_ad reserve_vds_ex; /* copy of main volume descriptor set ; 16 sectors min */
struct extent_ad next_vds_ex; /* points to the next block for volume descriptor space */
struct extent_ad vol_abstract;
struct extent_ad vol_copyright;
struct extent_ad integrity_seq_loc;
struct extent_ad alloc_desc[1];
struct extent_ad next_extent;
size = sizeof(struct extent_ad);
elmsz = sizeof(struct extent_ad);