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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 45C14C43381 for ; Tue, 5 Mar 2019 00:50:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E99720675 for ; Tue, 5 Mar 2019 00:50:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726170AbfCEAuY (ORCPT ); Mon, 4 Mar 2019 19:50:24 -0500 Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:17348 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726066AbfCEAuY (ORCPT ); Mon, 4 Mar 2019 19:50:24 -0500 Received: from ppp59-167-129-252.static.internode.on.net (HELO dastard) ([59.167.129.252]) by ipmail07.adl2.internode.on.net with ESMTP; 05 Mar 2019 11:20:22 +1030 Received: from dave by dastard with local (Exim 4.80) (envelope-from ) id 1h0yHk-000758-TD; Tue, 05 Mar 2019 11:50:20 +1100 Date: Tue, 5 Mar 2019 11:50:20 +1100 From: Dave Chinner To: Amir Goldstein Cc: fdmanana@kernel.org, fstests , Linux Btrfs , Filipe Manana Subject: Re: [PATCH] generic: add test for fsync after shrinking truncate and rename Message-ID: <20190305005020.GA26298@dastard> References: <20190304140622.23997-1-fdmanana@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Mar 04, 2019 at 05:04:23PM +0200, Amir Goldstein wrote: > On Mon, Mar 4, 2019 at 4:44 PM wrote: > > > > From: Filipe Manana > > > > Test that if we truncate a file to reduce its size, rename it and then > > fsync it, after a power failure the file has a correct size and name. > > > > I am not sure that ext4/xfs semantics guaranty anything about > persisting file name after fsync of file?... They do. It's that pesky "strictly ordered metadata" thing I keep having to explain to people... i.e. if you fsync an inode, then you are persisting all the changes needed to reference that file and it's data. And so if there was a rename in the history of that file, then that is persisted, too. Which means that both the original and the new directory modifications are persisted, too. *POSIX* doesn't require this - it says that if you O_DSYNC data, then it also includes all the metadata needed to reference that data. So even if the data is there, POSIX doesn't define whether the rename is there or noti, just that you can get to the fsync'd data via either the old or new name. IOWs, POSIX allows the behaviour to be implementation specific. In this case, file systems with strictly ordered metadata will end up making the rename visible because the rename occurred before the truncate that the fsync() is persisting... Cheers, Dave. -- Dave Chinner david@fromorbit.com