Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755734AbZC3Op2 (ORCPT ); Mon, 30 Mar 2009 10:45:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751520AbZC3OpL (ORCPT ); Mon, 30 Mar 2009 10:45:11 -0400 Received: from mx2.redhat.com ([66.187.237.31]:60045 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753221AbZC3OpJ (ORCPT ); Mon, 30 Mar 2009 10:45:09 -0400 Date: Mon, 30 Mar 2009 16:42:13 +0200 From: Andrea Arcangeli To: Alan Cox Cc: Matthew Garrett , Linus Torvalds , Theodore Tso , Ingo Molnar , Jan Kara , Andrew Morton , Arjan van de Ven , Peter Zijlstra , Nick Piggin , Jens Axboe , David Rees , Jesper Krogh , Linux Kernel Mailing List , Oleg Nesterov , Roland McGrath Subject: Re: [PATCH 2/2] Make relatime default Message-ID: <20090330144213.GA5426@random.random> References: <20090326090630.GA9369@elte.hu> <20090326113705.GV32307@mit.edu> <20090326140312.GB14822@elte.hu> <20090326144707.GA6239@mit.edu> <20090326170714.GF6239@mit.edu> <20090326174956.GB7198@srcf.ucam.org> <20090326175314.GC7198@srcf.ucam.org> <20090326184838.26166549@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090326184838.26166549@lxorguk.ukuu.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2123 Lines: 43 On Thu, Mar 26, 2009 at 06:48:38PM +0000, Alan Cox wrote: > On Thu, 26 Mar 2009 17:53:14 +0000 > Matthew Garrett wrote: > > > Change the default behaviour of the kernel to use relatime for all > > filesystems. This can be overridden with the "strictatime" mount > > option. > > NAK this again NAK but because if we change the default it is better to change it to the real thing: noatime. I think this can be solved in userland but perhaps changing this in kernel would be a stronger message that atime is officially obsoleted. (and nothing will break, not even mutt users will notice, and if they really do it won't be anything more than aesthetical) About the open(destination, O_TRUNC); write; close, I think it's not worth changing the kernel or the VM in any way to hide buggy programming like that, to the contrary it's great it was found early on (instead of being filed as some obscure not reproducible bug lost in some bugzilla and hitting once in a while with an unlucky power-loss during boot). But solving this bug with fsync so it works for writeback mode too, would make me prefer to gamble and run the the buggy version ;). Not sure if it worth providing any ordering guarantee more than 'ordered' mode in the long term or some proper barrier, but at least ordered mode already allows for renaming the tempfile to be enough and that is clearly the best tradeoff. fsync really should be used only to avoid total loss of information (like when we need to avoid losing the delivery of an email after the smpt client is told the email was already received by the smtp server). Using fsync to tell the kernel in what order to write is dirty pagecache data to disk, is as inefficient as driving a car to travel a 10 meters distance, so rightfully people isn't using it for this even if it's the only way it could work for writeback and ext2 too. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/