From patchwork Sun Apr 25 02:38:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12222955 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 4D99CC43461 for ; Sun, 25 Apr 2021 02:38:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D8EBC61482 for ; Sun, 25 Apr 2021 02:38:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8EBC61482 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 AE0126B006C; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A51B8D0001; 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 69F4C6B0070; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0067.hostedemail.com [216.40.44.67]) by kanga.kvack.org (Postfix) with ESMTP id 3E58D6B006E for ; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id DE1B58248047 for ; Sun, 25 Apr 2021 02:38:29 +0000 (UTC) X-FDA: 78069330738.03.2219855 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf09.hostedemail.com (Postfix) with ESMTP id 2EDB2600010B for ; Sun, 25 Apr 2021 02:38:23 +0000 (UTC) Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FSXF36bRQzpbTG; 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 10:38:17 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , Subject: [PATCH v4 2/4] swap: fix do_swap_page() race with swapoff Date: Sun, 25 Apr 2021 10:38:04 +0800 Message-ID: <20210425023806.3537283-3-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210425023806.3537283-1-linmiaohe@huawei.com> References: <20210425023806.3537283-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.104.174] X-CFilter-Loop: Reflected X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2EDB2600010B X-Stat-Signature: mnsbo5e7gcye6cdrdpbsgtw14rxo6hba Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf09; identity=mailfrom; envelope-from=""; helo=szxga04-in.huawei.com; client-ip=45.249.212.190 X-HE-DKIM-Result: none/none X-HE-Tag: 1619318303-322444 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: When I was investigating the swap code, I found the below possible race window: CPU 1 CPU 2 ----- ----- do_swap_page if (data_race(si->flags & SWP_SYNCHRONOUS_IO) swap_readpage if (data_race(sis->flags & SWP_FS_OPS)) { swapoff .. p->swap_file = NULL; .. struct file *swap_file = sis->swap_file; struct address_space *mapping = swap_file->f_mapping;[oops!] Note that for the pages that are swapped in through swap cache, this isn't an issue. Because the page is locked, and the swap entry will be marked with SWAP_HAS_CACHE, so swapoff() can not proceed until the page has been unlocked. Fix this race by using get/put_swap_device() to guard against concurrent swapoff. Fixes: 0bcac06f27d7 ("mm,swap: skip swapcache for swapin of synchronous device") Reported-by: kernel test robot (auto build test ERROR) Signed-off-by: Miaohe Lin Reviewed-by: "Huang, Ying" --- include/linux/swap.h | 9 +++++++++ mm/memory.c | 11 +++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index c9e7fea10b83..46d51d058d05 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -527,6 +527,15 @@ static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry) return NULL; } +static inline struct swap_info_struct *get_swap_device(swp_entry_t entry) +{ + return NULL; +} + +static inline void put_swap_device(struct swap_info_struct *si) +{ +} + #define swap_address_space(entry) (NULL) #define get_nr_swap_pages() 0L #define total_swap_pages 0L diff --git a/mm/memory.c b/mm/memory.c index 27014c3bde9f..39c910678387 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3311,6 +3311,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct page *page = NULL, *swapcache; + struct swap_info_struct *si = NULL; swp_entry_t entry; pte_t pte; int locked; @@ -3338,14 +3339,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) goto out; } + /* Prevent swapoff from happening to us. */ + si = get_swap_device(entry); + if (unlikely(!si)) + goto out; delayacct_set_flag(current, DELAYACCT_PF_SWAPIN); page = lookup_swap_cache(entry, vma, vmf->address); swapcache = page; if (!page) { - struct swap_info_struct *si = swp_swap_info(entry); - if (data_race(si->flags & SWP_SYNCHRONOUS_IO) && __swap_count(entry) == 1) { /* skip swapcache */ @@ -3514,6 +3517,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) unlock: pte_unmap_unlock(vmf->pte, vmf->ptl); out: + if (si) + put_swap_device(si); return ret; out_nomap: pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -3525,6 +3530,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) unlock_page(swapcache); put_page(swapcache); } + if (si) + put_swap_device(si); return ret; }