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 3143CC43470 for ; Tue, 20 Apr 2021 13:31:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E73B761027 for ; Tue, 20 Apr 2021 13:31:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232531AbhDTNc1 (ORCPT ); Tue, 20 Apr 2021 09:32:27 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:17802 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231718AbhDTNcS (ORCPT ); Tue, 20 Apr 2021 09:32:18 -0400 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4FPl022LFTzBrVN; Tue, 20 Apr 2021 21:29:22 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.498.0; Tue, 20 Apr 2021 21:31:36 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , Subject: [PATCH v3 0/4] close various race windows for swap Date: Tue, 20 Apr 2021 09:30:44 -0400 Message-ID: <20210420133048.6773-1-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.175] 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! 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 | 9 +++++ mm/shmem.c | 6 ++++ mm/swap_state.c | 6 ---- mm/swapfile.c | 79 +++++++++++++++++++++++++++----------------- 5 files changed, 76 insertions(+), 38 deletions(-) -- 2.19.1