From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262195AbTLDOU7 (ORCPT ); Thu, 4 Dec 2003 09:20:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262181AbTLDOU7 (ORCPT ); Thu, 4 Dec 2003 09:20:59 -0500 Received: from mail.fh-wedel.de ([213.39.232.194]:6789 "EHLO mail.fh-wedel.de") by vger.kernel.org with ESMTP id S262098AbTLDOU5 (ORCPT ); Thu, 4 Dec 2003 09:20:57 -0500 Date: Thu, 4 Dec 2003 15:17:25 +0100 From: =?iso-8859-1?Q?J=F6rn?= Engel To: Linus Torvalds Cc: Kallol Biswas , linux-kernel@vger.kernel.org, "linux-fsdevel@vger.kernel.org" Subject: Re: partially encrypted filesystem Message-ID: <20031204141725.GC7890@wohnheim.fh-wedel.de> References: <1070485676.4855.16.camel@nucleon> <20031203214443.GA23693@wohnheim.fh-wedel.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 3 December 2003 16:08:17 -0800, Linus Torvalds wrote: > On Wed, 3 Dec 2003, Jörn Engel wrote: > > > > Haven't heard about anything working yet, but it shouldn't be too hard > > to change something existing. For jffs2, I would guesstimate one or > > two month to add the necessary bits, but jffs2 is not first choice as > > a hard drive filesystem. Not sure about other filesystems. > > Encryption is not that easy to just tack on to most existing filesystems > for one simple reason: for performance (and memory footprint) reasons, > most of the filesystems out there are doing "IO in place". In other words, > they do IO directly into and directly from the page cache. > > With an encrypted filesystem, you can't do that. Or rather: you can do it > if the filesystem is read-only, but you definitely CANNOT do it on > writing. For writing you have to marshall the output buffer somewhere > else (and quite frankly, it tends to become a lot easier if you can do > that for reading too). Isn't that a problem already handled by all compressing filesystems? Or did I miss something really stupid? Jörn -- Optimizations always bust things, because all optimizations are, in the long haul, a form of cheating, and cheaters eventually get caught. -- Larry Wall