On Thu, Dec 28, 2023 at 7:26 AM Nhat Pham <nphamcs@xxxxxxxxx> wrote: > > On Wed, Dec 27, 2023 at 3:10 AM Barry Song <21cnbao@xxxxxxxxx> wrote: > > > > On Wed, Dec 27, 2023 at 5:16 PM Chengming Zhou > > <zhouchengming@xxxxxxxxxxxxx> wrote: > > > > > > Thanks for your explanation! Maybe it's best for us to return to 2 pages > > > if no other people's comments. And this really need more documentation :-) > > Fine by me. Hmm we're basically wasting one extra page per CPU (since > these buffers are per-CPU), correct? That's not ideal, but not *too* > bad for now I suppose... > > > > > I agree. we need some doc. > > > > besides, i actually think we can skip zswap frontend if > > over-compression is really > > happening. > > IIUC, zsmalloc already checked that - and most people are (or should > be) using zsmalloc for zswap anyway. I wouldn't be opposed to adding > an added layer of protection on the zswap side, but not super high > priority I'd say. Thanks for this info. I guess you mean the below ? unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp) { ... if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE)) return (unsigned long)ERR_PTR(-EINVAL); } i find zbud also has similar code: static int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp, unsigned long *handle) { int chunks, i, freechunks; struct zbud_header *zhdr = NULL; enum buddy bud; struct page *page; if (!size || (gfp & __GFP_HIGHMEM)) return -EINVAL; if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) return -ENOSPC; and z3fold, static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, unsigned long *handle) { int chunks = size_to_chunks(size); struct z3fold_header *zhdr = NULL; struct page *page = NULL; enum buddy bud; bool can_sleep = gfpflags_allow_blocking(gfp); if (!size || (gfp & __GFP_HIGHMEM)) return -EINVAL; if (size > PAGE_SIZE) return -ENOSPC; Thus, I agree that another layer to check size in zswap isn't necessary now. Thanks Barry