Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 26 Jul 2001 10:45:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 26 Jul 2001 10:45:20 -0400 Received: from pD951F257.dip.t-dialin.net ([217.81.242.87]:21637 "EHLO emma1.emma.line.org") by vger.kernel.org with ESMTP id ; Thu, 26 Jul 2001 10:45:11 -0400 Date: Thu, 26 Jul 2001 16:45:16 +0200 From: Matthias Andree To: Rik van Riel Cc: Alan Cox , Matthias Andree , Andrew Morton , lkml , "ext3-users@redhat.com" Subject: Re: ext3-2.4-0.9.4 Message-ID: <20010726164516.R17244@emma1.emma.line.org> Mail-Followup-To: Rik van Riel , Alan Cox , Andrew Morton , lkml , "ext3-users@redhat.com" In-Reply-To:

Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.3.19i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Original-Recipient: rfc822;linux-kernel-outgoing On Thu, 26 Jul 2001, Rik van Riel wrote: > An MTA which relies on this is therefore Broken(tm). MTAs rely on TRULY, ULTIMATELY AND DEFINITELY SYNCHRONOUS directory updates, nothing else. And because they do so, and most systems have them, and MTAs are portable, they choose chattr +S on Linux. And that's a performance problem because it doesn't come for free, but also with synchronous data updates, which are unnecessary because there is fsync(). That's already the complete story about MTAs on Linux. If Linux HAD a mode (it doesn't) to have just synchronous directory updates, MTAs could stop using chattr +S and be faster. MTAs do NOT care how the file system is internally managed, they only rely on the rename operation having completed physically on disk before the "my rename call has returned 0" event. They expect that with the call returning the rename operation has completed ultimately, finally, for good, definitely and the old file will not reappear after a crash. (Note that the atomicity addressed in the man pages and Unix specifications is a different one: it deals with the visibility of the changes in the system, not with the functioning of the file system.) That's why *BSD + softupdates is still recommended over Linux for pure mail transfer agents by people. This still implies the drive doesn't lie to the OS about the completion of write requests: write cache == off. -- Matthias Andree - 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/