From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0E11C433ED for ; Sun, 25 Apr 2021 09:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBC7B61164 for ; Sun, 25 Apr 2021 09:54:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229985AbhDYJzI (ORCPT ); Sun, 25 Apr 2021 05:55:08 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:3531 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229688AbhDYJzH (ORCPT ); Sun, 25 Apr 2021 05:55:07 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4FSjx721DgzRgwp; Sun, 25 Apr 2021 17:52:11 +0800 (CST) Received: from huawei.com (10.175.104.170) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Sun, 25 Apr 2021 17:54:23 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , Subject: [PATCH v5 0/4] close various race windows for swap Date: Sun, 25 Apr 2021 17:54:15 +0800 Message-ID: <20210425095419.3830298-1-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.170] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, When I was investigating the swap code, I found some possible race windows. This series aims to fix all these races. But using current get/put_swap_device() to guard against concurrent swapoff for swap_readpage() looks terrible because swap_readpage() may take really long time. And to reduce the performance overhead on the hot-path as much as possible, it appears we can use the percpu_ref to close this race window(as suggested by Huang, Ying). The patch 1 adds percpu_ref support for swap and most of the remaining patches try to use this to close various race windows. More details can be found in the respective changelogs. Thanks! v4->v5: collect Reviewed-by tag do put_swap_device() before returning from the function per Huang, Ying v3->v4: some commit log and comment enhance per Huang, Ying put get/put_swap_device() in shmem_swapin_page() per Huang, Ying collect Reviewed-by tag v2->v3: some commit log and comment enhance per Huang, Ying remove ref_initialized field squash PATCH 1-2 v1->v2: reorganize the patch-2/5 various enhance and fixup per Huang, Ying Many thanks for the comments of Huang, Ying, Dennis Zhou and Tim Chen. Miaohe Lin (4): mm/swapfile: use percpu_ref to serialize against concurrent swapoff swap: fix do_swap_page() race with swapoff mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info() mm/shmem: fix shmem_swapin() race with swapoff include/linux/swap.h | 14 ++++++-- mm/memory.c | 11 ++++-- mm/shmem.c | 12 +++++++ mm/swap_state.c | 6 ---- mm/swapfile.c | 79 +++++++++++++++++++++++++++----------------- 5 files changed, 82 insertions(+), 40 deletions(-) -- 2.23.0