From patchwork Tue Apr 20 13:30:44 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12214353 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 E3280C43460 for ; Tue, 20 Apr 2021 13:31:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 61E746113C for ; Tue, 20 Apr 2021 13:31:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61E746113C 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 444078E0001; Tue, 20 Apr 2021 09:31:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37FCA8D0001; Tue, 20 Apr 2021 09:31:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 270468E0001; Tue, 20 Apr 2021 09:31:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0134.hostedemail.com [216.40.44.134]) by kanga.kvack.org (Postfix) with ESMTP id 023738D0001 for ; Tue, 20 Apr 2021 09:31:56 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id B13FF3631 for ; Tue, 20 Apr 2021 13:31:56 +0000 (UTC) X-FDA: 78052833432.08.DC4C6D0 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf16.hostedemail.com (Postfix) with ESMTP id DF7B4801A817 for ; Tue, 20 Apr 2021 13:31:53 +0000 (UTC) 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 X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected X-Stat-Signature: 76hatat15b1x1hrarrj5bze4rbtqikyx X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DF7B4801A817 Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=szxga07-in.huawei.com; client-ip=45.249.212.35 X-HE-DKIM-Result: none/none X-HE-Tag: 1618925513-314668 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! 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(-)