MIN_IOS
ret = mempool_init_kmalloc_pool(&cc->req_pool, MIN_IOS, cc->dmreq_start + additional_req_size);
ret = bioset_init(&cc->bs, MIN_IOS, 0, BIOSET_NEED_BVECS);
ret = mempool_init_kmalloc_pool(&cc->tag_pool, MIN_IOS,
r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);