From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751691AbeE3Kjr (ORCPT ); Wed, 30 May 2018 06:39:47 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58900 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750904AbeE3Kjn (ORCPT ); Wed, 30 May 2018 06:39:43 -0400 From: Li Wang To: ddstreet@ieee.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Seth Jennings , Huang Ying , Yu Zhao Subject: [PATCH v2] zswap: re-check zswap_is_full after do zswap_shrink Date: Wed, 30 May 2018 18:39:36 +0800 Message-Id: <20180530103936.17812-1-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 in compressed pool. Reproduce steps: 1. Boot kernel with "zswap.enabled=1" 2. Set the max_pool_percent to 0 # echo 0 > /sys/module/zswap/parameters/max_pool_percent 3. Do memory stress test to see if some pages have been compressed # stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s 4. Watching the 'stored_pages' number increasing or not The root cause is: When zswap_max_pool_percent is setting to 0 via kernel parameter, the zswap_is_full() will always return true to do zswap_shrink(). But if the shinking is able to reclain a page successful, then proceeds to compress/store another page, so the value of stored_pages will keep changing. To solve the issue, this patch adds zswap_is_full() check again after zswap_shrink() to make sure it's now under the max_pool_percent, and not to compress/store if reach its limitaion. Signed-off-by: Li Wang Cc: Seth Jennings Cc: Dan Streetman Cc: Huang Ying Cc: Yu Zhao --- mm/zswap.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/zswap.c b/mm/zswap.c index 61a5c41..fd320c3 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1026,6 +1026,15 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset, ret = -ENOMEM; goto reject; } + + /* A second zswap_is_full() check after + * zswap_shrink() to make sure it's now + * under the max_pool_percent + */ + if (zswap_is_full()) { + ret = -ENOMEM; + goto reject; + } } /* allocate entry */ -- 2.9.5