On 2023/12/7 01:12, Nhat Pham wrote: > On Wed, Dec 6, 2023 at 1:46 AM Chengming Zhou > <zhouchengming@xxxxxxxxxxxxx> wrote: >> >> Maybe I missed something, but the dstmem size of 2 * PAGE_SIZE is >> very confusing, since we only need at most one page when compress, >> and the "dlen" is also PAGE_SIZE in acomp_request_set_params(). >> >> So change it to one page, and fix the comments. >> >> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> >> --- >> mm/zswap.c | 5 ++--- >> 1 file changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/mm/zswap.c b/mm/zswap.c >> index d93a7b58b5af..999671dcb469 100644 >> --- a/mm/zswap.c >> +++ b/mm/zswap.c >> @@ -699,7 +699,7 @@ static int zswap_dstmem_prepare(unsigned int cpu) >> struct mutex *mutex; >> u8 *dst; >> >> - dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); >> + dst = kmalloc_node(PAGE_SIZE, GFP_KERNEL, cpu_to_node(cpu)); >> if (!dst) >> return -ENOMEM; >> >> @@ -1649,8 +1649,7 @@ bool zswap_store(struct folio *folio) >> sg_init_table(&input, 1); >> sg_set_page(&input, page, PAGE_SIZE, 0); >> >> - /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */ >> - sg_init_one(&output, dst, PAGE_SIZE * 2); >> + sg_init_one(&output, dst, PAGE_SIZE); > > Hmm. This is very weird. It looks very intentional though, so perhaps > we should consult the maintainer or the original author of this logic > to double check this? Yes, it's also weird to me. But it seems to be 2 pages when the zswap code merged in mm 10 years ago. Hope the maintainer or author could shed some light on it. :) > My best guess is for cases where the compression algorithm fails - i.e > the output (header + payload) is somehow bigger than the original > data. But not sure if this happens at all, and if the size > PAGE_SIZE > we don't wanna store the output in zswap anyway. > Agree, so I think one page is enough. >> acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen); And here we just use PAGE_SIZE in the parameter actually. Thanks! >> /* >> * it maybe looks a little bit silly that we send an asynchronous request, >> >> -- >> b4 0.10.1
