From owner-freebsd-current@FreeBSD.ORG Sat Mar 31 06:15:46 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 9FDAD106564A for ; Sat, 31 Mar 2012 06:15:46 +0000 (UTC) (envelope-from matthias.andree@gmx.de) Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.22]) by mx1.freebsd.org (Postfix) with SMTP id 072F58FC0C for ; Sat, 31 Mar 2012 06:15:45 +0000 (UTC) Received: (qmail invoked by alias); 31 Mar 2012 06:15:44 -0000 Received: from g227125153.adsl.alicedsl.de (EHLO mandree.no-ip.org) [92.227.125.153] by mail.gmx.net (mp012) with SMTP; 31 Mar 2012 08:15:44 +0200 X-Authenticated: #428038 X-Provags-ID: V01U2FsdGVkX1/7HFJPL8j7mBuby7uWe8WFE/PjlXE8kaUGU7F5Lt m1NtWurJ9aXojQ Received: from [127.0.0.1] (localhost.localdomain [127.0.0.1]) by apollo.emma.line.org (Postfix) with ESMTP id 4416A23CEAF for ; Sat, 31 Mar 2012 08:15:44 +0200 (CEST) Message-ID: <4F76A110.4080002@gmx.de> Date: Sat, 31 Mar 2012 08:15:44 +0200 From: Matthias Andree User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.28) Gecko/20120313 Mnenhy/0.8.3 Thunderbird/3.1.20 MIME-Version: 1.0 To: freebsd-current@freebsd.org References: <4F746F1E.6090702@mail.zedat.fu-berlin.de> <4F74BCE8.2030802@vangyzen.net> <20120330.151848.41706133.sthaug@nethelp.no> In-Reply-To: X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Subject: Re: Using TMPFS for /tmp and /var/run? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 31 Mar 2012 06:15:46 -0000 Am 30.03.2012 21:36, schrieb Adrian Chadd: > Let me tell you a story. > > Someone decided that ext4 could have a decent speed up if it > implemented the posix standard for not flushing files on close(). > After all, if you needed it to be guaranteed to be written to disk, > you would call a flush routine first, before you called close(). > > So they did this. > > Then people testing out ext4 discovered that upon crash, their > kde/gnome profiles were corrupted. > > Why? Because KDE/Gnome authors hadn't ever called flush before > close(), and they weren't the only ones. They didn't read the > standard, they only used the system and fixed bugs whenever their > system behaved against their expectations. They didn't notice that the > system was being different from the standard. > > Guess what ext4 did? :) ext4 sprouted an option (auto_da_alloc, when used with the proper data journalling option data=ordered) to support buggy software. Note that ext4 isn't pioneering the "fsync() required" semantics here, there are other precedents of "0-blocks in files after crash" in Linux file systems, such as XFS. I'm oblivious to the current ext4 defaults WRT these semantics (and I haven't looked at vanilla kernels for a while anyways---distros might have changed default settings).