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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 BE4E7C83000 for ; Thu, 30 Apr 2020 01:11:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97AB62082E for ; Thu, 30 Apr 2020 01:11:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726561AbgD3BLy (ORCPT ); Wed, 29 Apr 2020 21:11:54 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:34866 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726291AbgD3BLy (ORCPT ); Wed, 29 Apr 2020 21:11:54 -0400 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 4C278CF36F6CE4FD2A34; Thu, 30 Apr 2020 09:11:48 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.204) with Microsoft SMTP Server (TLS) id 14.3.487.0; Thu, 30 Apr 2020 09:11:45 +0800 Subject: Re: [PATCH V3] f2fs: Avoid double lock for cp_rwsem during checkpoint To: Sayali Lokhande , , CC: , References: <1588179630-22819-1-git-send-email-sayalil@codeaurora.org> From: Chao Yu Message-ID: <7c68cd6d-d858-f80c-f258-e5e1340b9aa3@huawei.com> Date: Thu, 30 Apr 2020 09:11:43 +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: <1588179630-22819-1-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 2020/4/30 1:00, 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: > -close() > -iput() > iput(inode); > - f2fs_evict_inode() > - f2fs_truncate_blocks() > - f2fs_lock_op() > - down_read(&sbi->cp_rwsem); > > Fixes: 399368372ed9 ("f2fs: introduce a new global lock scheme") IMO, it should be 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data") It brings iput() to checkpoint process for the first time. Thanks, > Signed-off-by: Sayali Lokhande > --- > fs/f2fs/checkpoint.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > index 5ba649e..97b6378 100644 > --- a/fs/f2fs/checkpoint.c > +++ b/fs/f2fs/checkpoint.c > @@ -1219,21 +1219,19 @@ static int block_operations(struct f2fs_sb_info *sbi) > goto retry_flush_quotas; > } > > -retry_flush_nodes: > down_write(&sbi->node_write); > > if (get_pages(sbi, F2FS_DIRTY_NODES)) { > up_write(&sbi->node_write); > + up_write(&sbi->node_change); > + f2fs_unlock_all(sbi); > atomic_inc(&sbi->wb_sync_req[NODE]); > err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO); > atomic_dec(&sbi->wb_sync_req[NODE]); > - if (err) { > - up_write(&sbi->node_change); > - f2fs_unlock_all(sbi); > + if (err) > goto out; > - } > cond_resched(); > - goto retry_flush_nodes; > + goto retry_flush_quotas; > } > > /* >