From: Chris Worley Subject: RE: zero out blocks of freed user data for operation a virtual machine environment Date: Mon, 25 May 2009 11:26:15 -0600 Message-ID: References: <20090524170045.GC24753@cip.informatik.uni-erlangen.de> <20090524101551.57b706e9@infradead.org> <20090524173933.GD24753@cip.informatik.uni-erlangen.de> <20090525120320.GA25908@mit.edu> <20090525123430.GA5534@cip.informatik.uni-erlangen.de> <87ab51qq91.fsf@frosties.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: LKML , linux-ext4@vger.kernel.org Return-path: Received: from rv-out-0506.google.com ([209.85.198.229]:5458 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752851AbZEYRuo convert rfc822-to-8bit (ORCPT ); Mon, 25 May 2009 13:50:44 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, May 25, 2009 at 7:14 AM, Goswin von Brederlow wrote: > Thomas Glanzmann writes: > > Hello Ted, > > > >> Yes, it does, sb_issue_discard(). =A0So if you wanted to hook into= this > >> routine with a function which issued calls to zero out blocks, it > >> would be easy to create a private patch. > > > > that sounds good because it wouldn't only target the most used > > filesystem but every other filesystem that uses the interface as we= ll. > > Do you think that a tunable or configurable patch has a chance to h= it > > upstream as well? > > > > =A0 =A0 =A0 =A0 Thomas > > I could imagine a device mapper target that eats TRIM commands and > writes out zeroes instead. That should be easy to maintain outside or > inside the upstream kernel source. Why bother with a time-consuming performance-draining operation? There are devices that already support TRIM/discard commands today, and once you discard a block, it's completely irretrievable (you'll just get back zeros if you try to read that block w/o writing it after the discard). Chris > > > MfG > =A0 =A0 =A0 =A0Goswin -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html