ddt_phys_select
ddt_phys_t *ddp = ddt_phys_select(dde, bp);
extern ddt_phys_t *ddt_phys_select(const ddt_entry_t *dde, const blkptr_t *bp);
ddp = ddt_phys_select(dde, bp);
ddt_phys_t *ddp_self = ddt_phys_select(dde, bp);
ddp = ddt_phys_select(dde, bp);