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 065DCC43460 for ; Sun, 25 Apr 2021 02:38:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 91F53611C1 for ; Sun, 25 Apr 2021 02:38:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91F53611C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 86B106B0036; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7F6096B006E; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 623986B006C; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0037.hostedemail.com [216.40.44.37]) by kanga.kvack.org (Postfix) with ESMTP id 3241D6B006C for ; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id CEB8C18001163 for ; Sun, 25 Apr 2021 02:38:29 +0000 (UTC) X-FDA: 78069330738.24.D937745 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf28.hostedemail.com (Postfix) with ESMTP id 0AD3C2000255 for ; Sun, 25 Apr 2021 02:38:30 +0000 (UTC) Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FSXF35pmwzpbTB; Sun, 25 Apr 2021 10:35:19 +0800 (CST) Received: from huawei.com (10.175.104.174) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Sun, 25 Apr 2021 10:38:15 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , Subject: [PATCH v4 0/4] close various race windows for swap Date: Sun, 25 Apr 2021 10:38:02 +0800 Message-ID: <20210425023806.3537283-1-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.104.174] X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 0AD3C2000255 X-Stat-Signature: igepssczpry9a6upk7c9g8964cyega1t X-Rspamd-Server: rspam02 Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=szxga04-in.huawei.com; client-ip=45.249.212.190 X-HE-DKIM-Result: none/none X-HE-Tag: 1619318310-568481 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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! 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 | 11 ++++++ mm/swap_state.c | 6 ---- mm/swapfile.c | 79 +++++++++++++++++++++++++++----------------- 5 files changed, 81 insertions(+), 40 deletions(-) --=20 2.19.1