From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Li Wang , Dan Streetman , Seth Jennings , Huang Ying , Yu Zhao , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 057/165] zswap: re-check zswap_is_full() after do zswap_shrink() Date: Mon, 3 Sep 2018 18:55:43 +0200 Message-Id: <20180903165657.985743003@linuxfoundation.org> In-Reply-To: <20180903165655.003605184@linuxfoundation.org> References: <20180903165655.003605184@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Li Wang [ Upstream commit 16e536ef47f567289a5699abee9ff7bb304bc12d ] /sys/../zswap/stored_pages keeps rising in a zswap test with "zswap.max_pool_percent=0" parameter. But it should not compress or store pages any more since there is no space in the 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 set to 0 via kernel parameter, zswap_is_full() will always return true due to zswap_shrink(). But if the shinking is able to reclain a page successfully the code then proceeds to compressing/storing another page, so the value of stored_pages will keep changing. To solve the issue, this patch adds a zswap_is_full() check again after zswap_shrink() to make sure it's now under the max_pool_percent, and to not compress/store if we reached the limit. Link: http://lkml.kernel.org/r/20180530103936.17812-1-liwang@redhat.com Signed-off-by: Li Wang Acked-by: Dan Streetman Cc: Seth Jennings Cc: Huang Ying Cc: Yu Zhao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/zswap.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/mm/zswap.c +++ b/mm/zswap.c @@ -989,6 +989,15 @@ static int zswap_frontswap_store(unsigne 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 */