DRBD_MAGIC
h->magic = cpu_to_be32(DRBD_MAGIC);
*(__be32 *)header == cpu_to_be32(DRBD_MAGIC)) {
#define DRBD_MD_MAGIC_07 (DRBD_MAGIC+3)
#define DRBD_MD_MAGIC_08 (DRBD_MAGIC+4)
#define DRBD_MD_MAGIC_84_UNCLEAN (DRBD_MAGIC+5)