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=-8.2 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 05A59C38A2A for ; Sat, 9 May 2020 03:02:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE54021655 for ; Sat, 9 May 2020 03:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728651AbgEIDCf (ORCPT ); Fri, 8 May 2020 23:02:35 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:60608 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728353AbgEIDCe (ORCPT ); Fri, 8 May 2020 23:02:34 -0400 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 5A6CC335C76B1BBD74F7; Sat, 9 May 2020 11:02:32 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.208) with Microsoft SMTP Server (TLS) id 14.3.487.0; Sat, 9 May 2020 11:02:26 +0800 Subject: Re: [PATCH V4] f2fs: Avoid double lock for cp_rwsem during checkpoint To: Jaegeuk Kim , Sayali Lokhande CC: , , References: <1588244309-1468-1-git-send-email-sayalil@codeaurora.org> <20200508161052.GA49579@google.com> From: Chao Yu Message-ID: <0902037e-998d-812e-53e7-90ea7b9957eb@huawei.com> Date: Sat, 9 May 2020 11:02:25 +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: <20200508161052.GA49579@google.com> 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 2020/5/9 0:10, Jaegeuk Kim wrote: > Hi Sayali, > > In order to address the perf regression, how about this? > >>>From 48418af635884803ffb35972df7958a2e6649322 Mon Sep 17 00:00:00 2001 > From: Jaegeuk Kim > Date: Fri, 8 May 2020 09:08:37 -0700 > Subject: [PATCH] f2fs: avoid double lock for cp_rwsem during checkpoint > > 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: 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data") > Signed-off-by: Sayali Lokhande > Signed-off-by: Jaegeuk Kim > --- > fs/f2fs/node.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > index 1db8cabf727ef..626d7daca09de 100644 > --- a/fs/f2fs/node.c > +++ b/fs/f2fs/node.c > @@ -1870,8 +1870,8 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, > goto continue_unlock; > } > > - /* flush inline_data */ > - if (is_inline_node(page)) { > + /* flush inline_data, if it's not sync path. */ > + if (do_balance && is_inline_node(page)) { IIRC, this flow was designed to avoid running out of free space issue during checkpoint: 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data") The sceanrio is: 1. create fully node blocks 2. flush node blocks 3. write inline_data for all the node blocks again 4. flush node blocks redundantly I guess this may cause failing one case of fstest. Since block_operations->f2fs_sync_inode_meta has synced inode cache to inode page, so in block_operations->f2fs_sync_node_pages, could we check nlink before flush_inline_data(): if (is_inline_node(page)) { if (IS_INODE(page) && raw_inode_page->i_links) { flush_inline_data() } } > clear_inline_node(page); > unlock_page(page); > flush_inline_data(sbi, ino_of_node(page)); >