VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK
minimal_extra_space = 1 + (MAXIMUM_VDO_USER_VIOS / VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK);
((VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK - 1) / 8) + 1,
packed_slab_journal_entry entries[VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK];
journal->full_entries_per_block = VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK;