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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 EB512C4338F for ; Wed, 4 Aug 2021 03:29:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D252260F38 for ; Wed, 4 Aug 2021 03:29:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234902AbhHDDaE (ORCPT ); Tue, 3 Aug 2021 23:30:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:59022 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbhHDDaD (ORCPT ); Tue, 3 Aug 2021 23:30:03 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 01ACA61037; Wed, 4 Aug 2021 03:29:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628047791; bh=1iL1o2YZoGnWri3qeq+tQMAVLFgEuBeM6zTEgcD8x/0=; h=From:To:Cc:Subject:Date:From; b=BD4cCTnKHQ733Bo8SGheKl2MDcYfKXSpnoyI0seWn8Alagwcn3g+96Iz2Y28enleF NLlbvBJuabETpj8/cc2wf0aCJsYpE9g9UcUQX1ZrGcnSZXoLsRp31qcG7AaAQeNks+ p1s4Gr4xqJnXWVb83WiAh4TDmGPjG+zkNL1JsNRXl1wQ402czpwtQKo/cjb2egTikC 7hZsylN0GyKHbhLMeA67WL/GoO53ZUdpIK9nIcXx1UfbAsCPJUzXvNBdG/hgvsRZOp 5AUAq0VjIzypOyD5oR0Zrl7yQMGXHB2ceZ94TH+FVRNw64pPM3w79PAfJInFf7p313 Lkobbreq8o45g== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , Yangtao Li , Chao Yu Subject: [PATCH v4] f2fs: reduce the scope of setting fsck tag when de->name_len is zero Date: Wed, 4 Aug 2021 11:29:46 +0800 Message-Id: <20210804032946.1416807-1-chao@kernel.org> X-Mailer: git-send-email 2.22.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yangtao Li 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: ^ Thread A is traversing directory, ctx-pos moves to below position after readdir() by thread A: AAAABBBB___ ^ Then thread B delete dir_entry2, and create dir_entry3. Thread A calls readdir() to lookup dirents starting from middle of new dirent slots as below: AAAACCCCCC_ ^ 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 and b) before bit_pos moves to first valid dir_entry. Fixes: ddf06b753a85 ("f2fs: fix to trigger fsck if dirent.name_len is zero") Signed-off-by: Yangtao Li [Chao: clean up description] Reviewed-by: Chao Yu --- v4: - clean up description a bit - fix code style issue 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..c250bf46ef5e 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; 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) -- 2.22.1