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=-19.0 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=unavailable 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 85946C636C8 for ; Tue, 20 Jul 2021 10:28:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C16C61019 for ; Tue, 20 Jul 2021 10:28:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236354AbhGTJrZ (ORCPT ); Tue, 20 Jul 2021 05:47:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:58976 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237147AbhGTJmj (ORCPT ); Tue, 20 Jul 2021 05:42:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1515B610D2; Tue, 20 Jul 2021 10:23:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626776597; bh=rd+6u+6oPp2eEsaaxYZhuL9mvgQJhUujKnfnKSFFefA=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=RA8XyX3T6F5Q+lIzE+boh5ZoJJY8hEbdRkrpQlXNg1UFXSVQUygbS0Gtc7KGCoX5V PvkQaPcYhQygQa6rP9/PRp/N2WYilI6/eKy9RNo6C5nsln9TpTNjrkzAV76DfzwDi+ NlMYHmCxfyfhBgKdzv3+RZqmcKKn+m7Z6ZIpiGQVmkh70VhK7QeYLFjzEIltnvIpyK FuGWUb9+EScUh9DH6nB2itEytX6K6cJ5ZMd7VcFzGL8Coz1ILJGtRO2toxuh6Aheb9 BKmtOK9UMYFjnoVxs6G6BPsq+VKaH4kB6UIAtWT02bjNfyukjIEMlTRUK4oj6tlSEm 10yEm+fllu90Q== Subject: Re: [PATCH v3] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero To: Yangtao Li , jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20210720070633.337851-1-frank.li@vivo.com> From: Chao Yu Message-ID: <9f221a92-6c95-8f2f-a3d9-1d7abf5a6a6e@kernel.org> Date: Tue, 20 Jul 2021 18:23:15 +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: <20210720070633.337851-1-frank.li@vivo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 '^' > 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; Thanks, > int err = 0; > > bit_pos = ((unsigned long)ctx->pos % d->max); > @@ -1014,13 +1015,15 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, > > de = &d->dentry[bit_pos]; > if (de->name_len == 0) { > + if (found_valid_dirent || !bit_pos) { > + printk_ratelimited( > + "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", > + KERN_WARNING, sbi->sb->s_id, > + le32_to_cpu(de->ino)); > + set_sbi_flag(sbi, SBI_NEED_FSCK); > + } > bit_pos++; > ctx->pos = start_pos + bit_pos; > - printk_ratelimited( > - "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", > - KERN_WARNING, sbi->sb->s_id, > - le32_to_cpu(de->ino)); > - set_sbi_flag(sbi, SBI_NEED_FSCK); > continue; > } > > @@ -1063,6 +1066,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, > f2fs_ra_node_page(sbi, le32_to_cpu(de->ino)); > > ctx->pos = start_pos + bit_pos; > + found_valid_dirent = true; > } > out: > if (readdir_ra) >