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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE4A7C433F5 for ; Tue, 10 May 2022 13:40:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238581AbiEJNoY (ORCPT ); Tue, 10 May 2022 09:44:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243295AbiEJNaB (ORCPT ); Tue, 10 May 2022 09:30:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A79872C3346; Tue, 10 May 2022 06:21:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4CA4EB81DA3; Tue, 10 May 2022 13:21:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6794C385C2; Tue, 10 May 2022 13:21:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1652188881; bh=9AB0eIkm2p52mhcWgP0ARdREWpNnfAQ5M4KPSUn+kQw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Iz86m1RPI6xqLla01n9e0+p1Fe/vQFzUspTJ6j53HPGWdY5OVCzcDBj5NvV2/3HvN FjILaM1W6NNndpyBtBTrHyjvl1wiVfeVHpJsHQqcfiPK275PGo7kkPiTJR4LHE+CF6 2bAlAI0sOh0V3UtvQfm1XjA9wEfjlG8VNbnho+EI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Filipe Manana , David Sterba Subject: [PATCH 4.19 79/88] btrfs: always log symlinks in full mode Date: Tue, 10 May 2022 15:08:04 +0200 Message-Id: <20220510130736.023490077@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220510130733.735278074@linuxfoundation.org> References: <20220510130733.735278074@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Filipe Manana commit d0e64a981fd841cb0f28fcd6afcac55e6f1e6994 upstream. On Linux, empty symlinks are invalid, and attempting to create one with the system call symlink(2) results in an -ENOENT error and this is explicitly documented in the man page. If we rename a symlink that was created in the current transaction and its parent directory was logged before, we actually end up logging the symlink without logging its content, which is stored in an inline extent. That means that after a power failure we can end up with an empty symlink, having no content and an i_size of 0 bytes. It can be easily reproduced like this: $ mkfs.btrfs -f /dev/sdc $ mount /dev/sdc /mnt $ mkdir /mnt/testdir $ sync # Create a file inside the directory and fsync the directory. $ touch /mnt/testdir/foo $ xfs_io -c "fsync" /mnt/testdir # Create a symlink inside the directory and then rename the symlink. $ ln -s /mnt/testdir/foo /mnt/testdir/bar $ mv /mnt/testdir/bar /mnt/testdir/baz # Now fsync again the directory, this persist the log tree. $ xfs_io -c "fsync" /mnt/testdir $ mount /dev/sdc /mnt $ stat -c %s /mnt/testdir/baz 0 $ readlink /mnt/testdir/baz $ Fix this by always logging symlinks in full mode (LOG_INODE_ALL), so that their content is also logged. A test case for fstests will follow. CC: stable@vger.kernel.org # 4.9+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/tree-log.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4907,6 +4907,18 @@ static int btrfs_log_inode(struct btrfs_ } /* + * For symlinks, we must always log their content, which is stored in an + * inline extent, otherwise we could end up with an empty symlink after + * log replay, which is invalid on linux (symlink(2) returns -ENOENT if + * one attempts to create an empty symlink). + * We don't need to worry about flushing delalloc, because when we create + * the inline extent when the symlink is created (we never have delalloc + * for symlinks). + */ + if (S_ISLNK(inode->vfs_inode.i_mode)) + inode_only = LOG_INODE_ALL; + + /* * a brute force approach to making sure we get the most uptodate * copies of everything. */ @@ -5462,7 +5474,7 @@ process_leaf: } ctx->log_new_dentries = false; - if (type == BTRFS_FT_DIR || type == BTRFS_FT_SYMLINK) + if (type == BTRFS_FT_DIR) log_mode = LOG_INODE_ALL; ret = btrfs_log_inode(trans, root, BTRFS_I(di_inode), log_mode, 0, LLONG_MAX, ctx);