From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032391AbeEXKol (ORCPT ); Thu, 24 May 2018 06:44:41 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:35242 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S968277AbeEXJ55 (ORCPT ); Thu, 24 May 2018 05:57:57 -0400 From: Li Wang To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Seth Jennings , Dan Streetman , Huang Ying , Yu Zhao Subject: [PATCH RFC] zswap: reject to compress/store page if zswap_max_pool_percent is 0 Date: Thu, 24 May 2018 17:57:51 +0800 Message-Id: <20180524095752.17770-1-liwang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The '/sys/../zswap/stored_pages:' keep raising in zswap test with "zswap.max_pool_percent=0" parameter. But theoretically, it should not compress or store pages any more since there is no space for compressed pool. Reproduce steps: 1. Boot kernel with "zswap.enabled=1 zswap.max_pool_percent=17" 2. Set the max_pool_percent to 0 # echo 0 > /sys/module/zswap/parameters/max_pool_percent Confirm this parameter works fine # cat /sys/kernel/debug/zswap/pool_total_size 0 3. Do memory stress test to see if some pages have been compressed # stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s Watching the 'stored_pages' numbers increasing or not The root cause is: When the zswap_max_pool_percent is set to 0 via kernel parameter, the zswap_is_full() will always return true to shrink the pool size by zswap_shrink(). If the pool size has been shrinked a little success, zswap will do compress/store pages again. Then we get fails on that as above. Signed-off-by: Li Wang Cc: Seth Jennings Cc: Dan Streetman Cc: Huang Ying Cc: Yu Zhao --- mm/zswap.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/zswap.c b/mm/zswap.c index 61a5c41..2b537bb 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1007,6 +1007,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, u8 *src, *dst; struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) }; + if (!zswap_max_pool_percent) { + ret = -ENOMEM; + goto reject; + } + /* THP isn't supported */ if (PageTransHuge(page)) { ret = -EINVAL; -- 2.9.5