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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable 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 CB14CC433B4 for ; Mon, 26 Apr 2021 06:53:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A520561139 for ; Mon, 26 Apr 2021 06:53:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232070AbhDZGyb (ORCPT ); Mon, 26 Apr 2021 02:54:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231816AbhDZGya (ORCPT ); Mon, 26 Apr 2021 02:54:30 -0400 Received: from mail-wm1-x331.google.com (mail-wm1-x331.google.com [IPv6:2a00:1450:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EAC93C061574 for ; Sun, 25 Apr 2021 23:53:47 -0700 (PDT) Received: by mail-wm1-x331.google.com with SMTP id f15-20020a05600c4e8fb029013f5599b8a9so2501606wmq.1 for ; Sun, 25 Apr 2021 23:53:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Pztt8Wk71RNkkzrtl1o4xHEFmBSxcCXDlHqJEhnOJyQ=; b=G2qaGHSCvHB8XzskGhObrZ+o21NjyHuWiSPY9heAoJtFitrVC93R69xTJ0bBVdKZRo AKQcW0np83kB9sTonB3jz3iP/tvnobwthsbTgPbqiSe3K15hC5V3Mn3yh86o470gM5cn WBDZUNrMdw7/cdVODZXS13A/taiWLZjatvQLhxaqlo9ivGAABRoMGkOv/snePeJHF5WN v7CpsxHm+Tl3lSQvdRdksApwdstSyFKYonKl11auAYtCyvQFzxGytQ9nDlqjUXSjjowh mAXMyIixVuAPHKnUtDd9SCqvCpBuoe/0P/D8DGlpK7iB7XZHRDZhsnN97gMpRDOVDBXv 3CFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Pztt8Wk71RNkkzrtl1o4xHEFmBSxcCXDlHqJEhnOJyQ=; b=nHYJIYCuSMdkscRo3itHK2VlfbAdtVfb3oxD6fbqEaZOTFwqYiDFjpPVDHXCOSvE2X Ws5D8X/uZJO7vpcsy8WBzOZsgWdrGcni95I7ZVpnmbZAr+NiGrCnu57sOJ2OR8UtYbb3 HK0IVuw7msKjpaDMN6xTp+zkVYHj+lTu70KYu3n7B929eR5ZxYGmqs5F/Fv6OUu61yde Slds/zcPJ8pwzDT6gUT4yaN6sEmfnQoluPowHBRK8NnG5luxFxWcEskcdwCua0OT956Y r+hwXIQIlY9Lnvartkkqo/xNQo/avmUBFvq+1zJ9jFWpeVv+nz7nkMRBIepnfjKJ3NoN mX7w== X-Gm-Message-State: AOAM532SKl07gK0/HRBW7ycTQIB4crWU2694p0nruemG705sm1IaIvq3 6oQpn/EirgDNlx3BYOVITZWsaDh5Guhw1gOA4dpsUg== X-Google-Smtp-Source: ABdhPJzXdTIZWGLS1AdpPGVNLIa863MGLencqacznclQQcOLxUQlH3JZO3gpprcqrzyQz1s9NcwyEzb0MbAptbPeJrQ= X-Received: by 2002:a1c:4e01:: with SMTP id g1mr18641817wmh.48.1619420026371; Sun, 25 Apr 2021 23:53:46 -0700 (PDT) MIME-Version: 1.0 References: <20210425095419.3830298-1-linmiaohe@huawei.com> <20210425095419.3830298-5-linmiaohe@huawei.com> In-Reply-To: <20210425095419.3830298-5-linmiaohe@huawei.com> From: Yu Zhao Date: Mon, 26 Apr 2021 00:53:34 -0600 Message-ID: Subject: Re: [PATCH v5 4/4] mm/shmem: fix shmem_swapin() race with swapoff To: Miaohe Lin Cc: Andrew Morton , Huang Ying , dennis@kernel.org, Tim Chen , Hugh Dickins , Johannes Weiner , Michal Hocko , Joonsoo Kim , alexs@kernel.org, Matthew Wilcox , Minchan Kim , Wei Yang , Yang Shi , David Hildenbrand , linux-kernel , Linux-MM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 25, 2021 at 3:54 AM Miaohe Lin wrote: > > When I was investigating the swap code, I found the below possible race > window: > > CPU 1 CPU 2 > ----- ----- > shmem_swapin > swap_cluster_readahead > if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) { > swapoff > .. > si->swap_file = NULL; > .. > struct inode *inode = si->swap_file->f_mapping->host;[oops!] > > Close this race window by using get/put_swap_device() to guard against > concurrent swapoff. > > Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not") > Signed-off-by: Miaohe Lin > --- > mm/shmem.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 26c76b13ad23..2dafd65b0b42 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1696,6 +1696,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, > struct address_space *mapping = inode->i_mapping; > struct shmem_inode_info *info = SHMEM_I(inode); > struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm; > + struct swap_info_struct *si; > struct page *page; > swp_entry_t swap; > int error; > @@ -1704,6 +1705,12 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, > swap = radix_to_swp_entry(*pagep); > *pagep = NULL; > > + /* Prevent swapoff from happening to us. */ > + si = get_swap_device(swap); > + if (!si) { > + error = EINVAL; > + goto failed; > + } page is uninitialized? > /* Look it up and read it in.. */ > page = lookup_swap_cache(swap, NULL, 0); > if (!page) { > @@ -1765,6 +1772,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, > swap_free(swap); > > *pagep = page; > + if (si) > + put_swap_device(si); > return 0; > failed: > if (!shmem_confirm_swap(mapping, index, swap)) > @@ -1775,6 +1784,9 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, > put_page(page); > } > > + if (si) > + put_swap_device(si); > + > return error; > } > > -- > 2.23.0 > >