VDO_SLAB_JOURNAL_PAYLOAD_SIZE
VDO_SLAB_JOURNAL_FULL_ENTRIES_PER_BLOCK = (VDO_SLAB_JOURNAL_PAYLOAD_SIZE * 8) / 25,
(VDO_SLAB_JOURNAL_PAYLOAD_SIZE / sizeof(packed_slab_journal_entry)),
u8 space[VDO_SLAB_JOURNAL_PAYLOAD_SIZE];