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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8F42BC433ED for ; Mon, 26 Apr 2021 00:56:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 634D16102A for ; Mon, 26 Apr 2021 00:56:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231559AbhDZA4s (ORCPT ); Sun, 25 Apr 2021 20:56:48 -0400 Received: from mga02.intel.com ([134.134.136.20]:61330 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231247AbhDZA4s (ORCPT ); Sun, 25 Apr 2021 20:56:48 -0400 IronPort-SDR: 6xtyxkuInOlL/96WVUjtr3A+ciUhCcpDsguufVkcBHX/nQQsd3WyLOreUdKaosSPvVb2zjqTGR POuDKekh+ZHQ== X-IronPort-AV: E=McAfee;i="6200,9189,9965"; a="183398203" X-IronPort-AV: E=Sophos;i="5.82,251,1613462400"; d="scan'208";a="183398203" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2021 17:56:06 -0700 IronPort-SDR: O7fvrG/uZjaFVoQyOH5zf8WJ+n29SIr4OjZdnc0pILVRSO84WuMgdE3xXPqmvCK1cCUkBqVZGa YdL1K5IvJXeg== X-IronPort-AV: E=Sophos;i="5.82,251,1613462400"; d="scan'208";a="422410038" Received: from yhuang6-desk1.sh.intel.com (HELO yhuang6-desk1.ccr.corp.intel.com) ([10.239.13.1]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2021 17:56:02 -0700 From: "Huang, Ying" To: Miaohe Lin Cc: , , , , , , , , , , , , , , Subject: Re: [PATCH v5 4/4] mm/shmem: fix shmem_swapin() race with swapoff References: <20210425095419.3830298-1-linmiaohe@huawei.com> <20210425095419.3830298-5-linmiaohe@huawei.com> Date: Mon, 26 Apr 2021 08:56:00 +0800 In-Reply-To: <20210425095419.3830298-5-linmiaohe@huawei.com> (Miaohe Lin's message of "Sun, 25 Apr 2021 17:54:19 +0800") Message-ID: <87pmyhx3rz.fsf@yhuang6-desk1.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miaohe Lin writes: > 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 Thanks! Reviewed-by: "Huang, Ying" > --- > 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; > + } > /* 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; > }