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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 4D927C43382 for ; Thu, 27 Sep 2018 22:49:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05771216E3 for ; Thu, 27 Sep 2018 22:49:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05771216E3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lxorguk.ukuu.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728364AbeI1FJp (ORCPT ); Fri, 28 Sep 2018 01:09:45 -0400 Received: from www.llwyncelyn.cymru ([82.70.14.225]:58492 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726024AbeI1FJp (ORCPT ); Fri, 28 Sep 2018 01:09:45 -0400 Received: from alans-desktop (82-70-14-226.dsl.in-addr.zen.co.uk [82.70.14.226]) by fuzix.org (8.15.2/8.15.2) with ESMTP id w8RMmxLL000501; Thu, 27 Sep 2018 23:48:59 +0100 Date: Thu, 27 Sep 2018 23:48:58 +0100 From: Alan Cox To: "Theodore Y. Ts'o" Cc: Jeff Layton , =?UTF-8?B?54Sm5pmT5Yas?= , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Rogier Wolff Subject: Re: POSIX violation by writeback error Message-ID: <20180927234858.507ea60b@alans-desktop> In-Reply-To: <20180926214909.GD3688@thunk.org> References: <486f6105fd4076c1af67dae7fdfe6826019f7ff4.camel@redhat.com> <20180925003044.239531c7@alans-desktop> <0662a4c5d2e164d651a6a116d06da380f317100f.camel@redhat.com> <20180925154627.GC2933@thunk.org> <23cd68a665d27216415dc79367ffc3bee1b60b86.camel@redhat.com> <20180925223054.GH2933@thunk.org> <20180926191055.6fc1514f@alans-desktop> <20180926214909.GD3688@thunk.org> Organization: Intel Corporation X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 26 Sep 2018 17:49:09 -0400 "Theodore Y. Ts'o" wrote: > On Wed, Sep 26, 2018 at 07:10:55PM +0100, Alan Cox wrote: > > In almost all cases you don't care so you wouldn't use it. In those cases > > where it might matter it's almost always the case that a reader won't > > consume it before it hits the media. > > > > That's why I suggested having an fbarrier() so you can explicitly say 'in > > the even that case does happen then stall and write it'. It's kind of > > lazy fsync. That can be used with almost no cost by things like mail > > daemons. > > How could mail daemons use it? They *have* to do an fsync() before > they send a 2xx SMTP return code. Point - so actually it would be less useful > > Another way given that this only really makes sense with locks > > is to add that fbarrier notion as a file locking optional semantic so you > > can 'unlock with barrier' and 'lock with barrier honoured' > > I'm not sure what you're suggesting? If someone has an actual case you could in theory constrain it to a range specified in a file lock and only between two people who care. That said seems like a lot of complexity to make a case nobody cares about only affect people who care about it Alan