From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: [RFC][PATCH 0/2]Extend ext3 filesystem limit from 8TB to 16TB Date: Thu, 30 Mar 2006 10:36:37 -0700 Message-ID: <20060330173637.GV5030@schatzie.adilger.int> References: <20060325223358sho@rifu.tnes.nec.co.jp> <1143485147.3970.23.camel@dyn9047017067.beaverton.ibm.com> <20060327131049.2c6a5413.akpm@osdl.org> <20060327225847.GC3756@localhost.localdomain> <1143530126.11560.6.camel@openx2.frec.bull.fr> <1143568905.3935.13.camel@dyn9047017067.beaverton.ibm.com> <1143623605.5046.11.camel@openx2.frec.bull.fr> <1143682730.4045.145.camel@dyn9047017067.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , Takashi Sato , Laurent Vivier , linux-kernel@vger.kernel.org, ext2-devel , linux-fsdevel@vger.kernel.org Return-path: Received: from mail.clusterfs.com ([206.168.112.78]:2540 "EHLO mail.clusterfs.com") by vger.kernel.org with ESMTP id S1750923AbWC3Rgk (ORCPT ); Thu, 30 Mar 2006 12:36:40 -0500 To: Mingming Cao Content-Disposition: inline In-Reply-To: <1143682730.4045.145.camel@dyn9047017067.beaverton.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mar 29, 2006 17:38 -0800, Mingming Cao wrote: > There are places in ext3 code to use "int" to represent block numbers in > kernel(not on-disk). This seems the "only" reason that why we can only > have 8TB ext3 rather than 16TB. Most times it just a bug with no > particular reason why not use unsigned 32 bit value, so the fix is easy. > > However, it is not so straightforward fix for the ext3 block allocation > code, as ext3_new_block() returns a block number, and "-1" to indicating > block allocation failure. Ext3 block reservation code, called by > ext3_new_block(), thus also use "int" for block numbers in some places. What might make the code a lot clearer, easier to audit, and easier to fix in the future is to declare new types for fs block offsets and group block offsets. Something like "ext3_fsblk" and "ext3_grblk". That way, we can declare ext3_fsblk as "unsigned long" and "ext3_grblk" as "unsigned int", and we could optionally change ext3_fsblk to be "unsigned long long" later to support 64-bit filesystems without having to re-patch all of the code. It would be more clear what type of block offset a function is handling (fs-wide or group-relative). If we wanted to be able to overload the block number with an error code we could use ERR_PTR and PTR_ERR like macros, and just restrict the filesystem to 2^32 - 1024 blocks until we extend it to 64 bits. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.