From patchwork Sat Apr 17 09:40:34 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12209611 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 D7F78C433ED for ; Sat, 17 Apr 2021 09:41:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 309EA611EF for ; Sat, 17 Apr 2021 09:41:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 309EA611EF 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 5CB1E6B006C; Sat, 17 Apr 2021 05:41:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 57CC16B006E; Sat, 17 Apr 2021 05:41:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 445346B0070; Sat, 17 Apr 2021 05:41:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0185.hostedemail.com [216.40.44.185]) by kanga.kvack.org (Postfix) with ESMTP id 248AB6B006C for ; Sat, 17 Apr 2021 05:41:49 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C5537180ACF7F for ; Sat, 17 Apr 2021 09:41:48 +0000 (UTC) X-FDA: 78041367096.27.98041F0 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) by imf28.hostedemail.com (Postfix) with ESMTP id D8EE82000255 for ; Sat, 17 Apr 2021 09:41:49 +0000 (UTC) Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FMp2b4JhZzlYjX; Sat, 17 Apr 2021 17:39:51 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Sat, 17 Apr 2021 17:41:36 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH v2 0/5] close various race windows for swap Date: Sat, 17 Apr 2021 05:40:34 -0400 Message-ID: <20210417094039.51711-1-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: n4c3sj93gt9dnd97kqhxpbberfm5x5rk X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D8EE82000255 Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=szxga06-in.huawei.com; client-ip=45.249.212.32 X-HE-DKIM-Result: none/none X-HE-Tag: 1618652509-64593 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000032, 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! 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 (5): mm/swapfile: add percpu_ref support for swap 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 | 15 +++++++-- mm/memory.c | 9 ++++++ mm/shmem.c | 6 ++++ mm/swap_state.c | 6 ---- mm/swapfile.c | 74 +++++++++++++++++++++++++++----------------- 5 files changed, 73 insertions(+), 37 deletions(-)