Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754304Ab3GYBI0 (ORCPT ); Wed, 24 Jul 2013 21:08:26 -0400 Received: from longford.logfs.org ([213.229.74.203]:59897 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752569Ab3GYBIX (ORCPT ); Wed, 24 Jul 2013 21:08:23 -0400 Date: Wed, 24 Jul 2013 19:36:28 -0400 From: =?utf-8?B?SsO2cm4=?= Engel To: Dhaval Giani Cc: linux-kernel@vger.kernel.org, tytso@mit.edu, tglek@mozilla.com, vdjeric@mozilla.com, glandium@mozilla.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC/PATCH 0/2] ext4: Transparent Decompression Support Message-ID: <20130724233628.GD3641@logfs.org> References: <1374699833.7083.2.camel@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1374699833.7083.2.camel@localhost> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1765 Lines: 41 On Wed, 24 July 2013 17:03:53 -0400, Dhaval Giani wrote: > > I am posting this series early in its development phase to solicit some > feedback. At this state, a good description of the format would be nice. > We are implementing transparent decompression with a focus on ext4. One > of the main usecases is that of Firefox on Android. Currently libxul.so > is compressed and it is loaded into memory by a custom linker on > demand. With the use of transparent decompression, we can make do > without the custom linker. More details (i.e. code) about the linker can > be found at https://github.com/glandium/faulty.lib It is not quite clear what you want to achieve here. One approach is to create an empty file, chattr it to enable compression, then write uncompressed data to it. Nothing in userspace will ever know the file is compressed, unless you explicitly call lsattr. If you want to follow some other approach where userspace has one interface to write the compressed data to a file and some other interface to read the file uncompressed, you are likely in a world of pain. Assuming you use the chattr approach, that pretty much comes down to adding compression support to ext4. There have been old patches for ext2 around that never got merged. Reading up on the problems encountered by those patches might be instructive. Jörn -- I've never met a human being who would want to read 17,000 pages of documentation, and if there was, I'd kill him to get him out of the gene pool. -- Joseph Costello -- 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/