From: Dave Chinner Subject: Re: [RFC] Add new extent structure in ext4 Date: Thu, 26 Jan 2012 09:48:47 +1100 Message-ID: <20120125224847.GT15102@dastard> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ted Ts'o , Andreas Dilger , Ext4 Developers List To: Robin Dong Return-path: Received: from ipmail04.adl6.internode.on.net ([150.101.137.141]:45764 "EHLO ipmail04.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772Ab2AYWsu (ORCPT ); Wed, 25 Jan 2012 17:48:50 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Jan 23, 2012 at 08:51:53PM +0800, Robin Dong wrote: > Hi Ted, Andreas and the list, > > After the bigalloc-feature is completed in ext4, we could have much more > big size of block-group (also bigger continuous space), but the extent > structure of files now limit the extent size below 128MB, which is not > optimal. > > We could solve the problem by creating a new extent format to support > larger extent size, which looks like this: > > struct ext4_extent2 { > __le64 ee_block; /* first logical block extent covers */ > __le64 ee_start; /* starting physical block */ > __le32 ee_len; /* number of blocks covered by extent */ > __le32 ee_flags; /* flags and future extension */ > }; > > struct ext4_extent2_idx { > __le64 ei_block; /* index covers logical blocks from 'block' */ > __le64 ei_leaf; /* pointer to the physical block of the next level */ > __le32 ei_flags; /* flags and future extension */ > __le32 ei_unused; /* padding */ > }; > > I think we could keep the structure of ext4_extent_header and add new > imcompat flag EXT4_FEATURE_INCOMPAT_EXTENTS2. > > The new extent format could support 16TB continuous space and larger volumes. > > What's your opinion? Just use XFS. Cheers, Dave. -- Dave Chinner david@fromorbit.com