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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 4FB7FC54FD0 for ; Mon, 27 Apr 2020 06:08:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F050206A5 for ; Mon, 27 Apr 2020 06:08:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726434AbgD0GIr (ORCPT ); Mon, 27 Apr 2020 02:08:47 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:51230 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726221AbgD0GIr (ORCPT ); Mon, 27 Apr 2020 02:08:47 -0400 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 3D62DCE1779533C62C14; Mon, 27 Apr 2020 14:08:45 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.202) with Microsoft SMTP Server (TLS) id 14.3.487.0; Mon, 27 Apr 2020 14:08:40 +0800 Subject: Re: [PATCH V2] f2fs: Avoid double lock for cp_rwsem during checkpoint To: Sayali Lokhande , , CC: , References: <1587967204-24824-1-git-send-email-sayalil@codeaurora.org> From: Chao Yu Message-ID: <6cfb8f00-a36c-03b9-ffa7-12fe37a19317@huawei.com> Date: Mon, 27 Apr 2020 14:08:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1587967204-24824-1-git-send-email-sayalil@codeaurora.org> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/4/27 14:00, Sayali Lokhande wrote: > There could be a scenario where f2fs_sync_node_pages gets > called during checkpoint, which in turn tries to flush > inline data and calls iput(). This results in deadlock as > iput() tries to hold cp_rwsem, which is already held at the > beginning by checkpoint->block_operations(). > > Call stack : > > Thread A Thread B > f2fs_write_checkpoint() > - block_operations(sbi) > - f2fs_lock_all(sbi); > - down_write(&sbi->cp_rwsem); > > - open() > - igrab() > - write() write inline data > - unlink() > - f2fs_sync_node_pages() > - if (is_inline_node(page)) > - flush_inline_data() > - ilookup() > page = f2fs_pagecache_get_page() > if (!page) > goto iput_out; > iput_out: > > - iput() ^^^^ - close() - iput() > iput(inode); > - f2fs_evict_inode() > - f2fs_truncate_blocks() > - f2fs_lock_op() > - down_read(&sbi->cp_rwsem); > > Signed-off-by: Sayali Lokhande Reviewed-by: Chao Yu Thanks,