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=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 96B89C4338F for ; Wed, 4 Aug 2021 03:33:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F19461040 for ; Wed, 4 Aug 2021 03:33:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234388AbhHDDdQ (ORCPT ); Tue, 3 Aug 2021 23:33:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:60986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbhHDDdO (ORCPT ); Tue, 3 Aug 2021 23:33:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 81E5D61037; Wed, 4 Aug 2021 03:33:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628047982; bh=L4lrzLbH/aV3W5MjROtpuPqG8ncWOO07RWA08kmI+ts=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=YFUuXXyxGoUyT/b0+YHP3RTRGNkE+kReB/vVxSbZ9sv/8Vuip8FzQgUGMK/AZrmnt QSVtIyrxIGicFU7jbEp6fBH+dXKLBhMtr0o12DNRs4d7RapJG/F7KveUqSJgm8NCCv Lvzcn6+28XC6Vc2F13mb5tu2I+4p8hHCdAyDYK9z5C4NBry6n3+hAhoGxLBcKC0zNc Mc+ziXtOOHrqwh9zBbeE4zZ2U9EB3dx4kxGR+sqL3Cq+68gLDq9Chf0ug8cEg2FzRJ q8+ebDbGgtLc6n75TobFfTL1rzI8YEzC6shta9zzjDbU/SM2i+3fKAVKOKwwl/LAnn r+3xLXV9TxERg== Subject: Re: [PATCH v3] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero To: =?UTF-8?B?5p2O5oms6Z+s?= Cc: jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: From: Chao Yu Message-ID: <2c59c14b-008c-aee9-6775-13b47fbd252f@kernel.org> Date: Wed, 4 Aug 2021 11:32:59 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Yangtao, I did some cleanup in your patch, and resend for you, please note that. :) Thanks, On 2021/7/20 20:31, 李扬韬 wrote: > HI Chao， > > From: Chao Yu > Date: 2021-07-20 18:23:15 > To: Yangtao Li ,jaegeuk@kernel.org > Cc: linux-f2fs-devel@lists.sourceforge.net,linux-kernel@vger.kernel.org > Subject: Re: [PATCH v3] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero>On 2021/7/20 15:06, Yangtao Li wrote: >>> I recently found a case where de->name_len is 0 in f2fs_fill_dentries() easily reproduced, >>> and finally set the fsck flag. >>> >>> Thread A Thread B >>> >>> f2fs_readdir >>> f2fs_read_inline_dir >>> ctx->pos = d.max >>> f2fs_add_dentry >>> f2fs_add_inline_entry >>> do_convert_inline_dir >>> f2fs_add_regular_entry >>> f2fs_readdir >>> f2fs_fill_dentries >>> set_sbi_flag(sbi, SBI_NEED_FSCK) >>> >>> Process A opens the folder, and has been reading without closing it. During this period, >>> Process B created a file under the folder (occupying multiple f2fs_dir_entry, exceeding >>> the d.max of the inline dir). After creation, process A uses the d.max of inline dir to >>> read it again, and it will read that de->name_len is 0. >>> >>> And Chao pointed out that w/o inline conversion, the race condition still can happen as below >>> >>> dir_entry1: A >>> dir_entry2: B >>> dir_entry3: C >>> free slot: _ >>> ctx->pos: ^ >>> >>> Before: >>> AAAABBBB___ >>> ^ >> >> please use blank instead of tab before '^' > > I don't know exactly what happened. In fact, in v2, spaces were used. Then it was changed to tab in v3. > >> >>> Thread B delete dir_entry2, and create dir_entry3. >>> >>> After: >>> AAAACCCCC__ >>> ^ >> >> Ditto >> >>> >>> In these scenarios, the file system is not damaged, and it's hard to avoid it. But we can bypass >>> tagging FSCK flag if: >>> a) bit_pos (:= ctx->pos % d->max) is non-zero & b) before bit_pos moves to first >>> valid dir_entry. >>> >>> Signed-off-by: Yangtao Li >>> --- >>> fs/f2fs/dir.c | 14 +++++++++----- >>> 1 file changed, 9 insertions(+), 5 deletions(-) >>> >>> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c >>> index 456651682daf..bfe942733b5e 100644 >>> --- a/fs/f2fs/dir.c >>> +++ b/fs/f2fs/dir.c >>> @@ -1000,6 +1000,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, >>> struct f2fs_sb_info *sbi = F2FS_I_SB(d->inode); >>> struct blk_plug plug; >>> bool readdir_ra = sbi->readdir_ra == 1; >>> + bool found_valid_dirent = false; >> >> One more blank before '='. >> >> bool found_valid_dirent = false; >> > > OK. > > Thx， > > >