VDO_SLAB_SUMMARY_ENTRIES_PER_BLOCK
VDO_SLAB_SUMMARY_BLOCKS_PER_ZONE = MAX_VDO_SLABS / VDO_SLAB_SUMMARY_ENTRIES_PER_BLOCK,
u8 index = slab->slab_number / VDO_SLAB_SUMMARY_ENTRIES_PER_BLOCK;
block->entries = &allocator->summary_entries[VDO_SLAB_SUMMARY_ENTRIES_PER_BLOCK * index];