From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: [PATCH 2/3] Fix problems on multi-TB filesystem and file Date: Fri, 13 Jan 2006 13:51:52 -0700 Message-ID: <20060113205152.GD7641@schatzie.adilger.int> References: <20060112183319.526b877a.akpm@osdl.org> <000101c61848$4dd3b5b0$4168010a@bsd.tnes.nec.co.jp> <20060113122820.18b751b0.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Takashi Sato , torvalds@osdl.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, trond.myklebust@fys.uio.no Return-path: Received: from moraine.clusterfs.com ([66.96.26.190]:2176 "EHLO moraine.clusterfs.com") by vger.kernel.org with ESMTP id S1422955AbWAMUvy (ORCPT ); Fri, 13 Jan 2006 15:51:54 -0500 To: Andrew Morton Content-Disposition: inline In-Reply-To: <20060113122820.18b751b0.akpm@osdl.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Jan 13, 2006 12:28 -0800, Andrew Morton wrote: > So now we're proposing to repeat the sector_t problem with a bunch of new > fields. Fortunately we're less likely to be putting these particular > fields into printk statements but I note that CIFS (at least) has a couple > such statements and with your patch they're now generating warnings (and > potential runtime bugs). > > On the other hand, for a fairly fat .config which has 17 filesystems in > .vmlinux: > > text data bss dec hex filename > 4633032 1011304 248288 5892624 59ea10 vmlinux CONFIG_LSF=y > 4633680 1011304 248288 5893272 59ec98 vmlinux CONFIG_LSF=n > > It's probably less 0.5 kbytes for usual embedded .config. > I just don't think the benefit of CONFIG_LSF outweighs its costs. We were originally going to use CONFIG_LBD, but there were some complaints that "sector_t" isn't the right variable to use for this, even though they are remarkably close. That would at least remove one config change. I don't think the cost is in the vmlinux itself, but rather that having a long long for i_blocks is overkill for any but the very largest systems (Lustre has been running fine w/o this, at the expense of some accuracy for the i_blocks count on many-TB files). Growing struct inode for these 0.0000001% of systems is probably harmful for small systems, given how many inodes are used in a system. Two options exist IMHO: - remove the new CONFIG_* parameters and stick with CONFIG_LBD (this could still use a separate type from sector_t if desired) to reduce the amount of testing combinations needed - make the new CONFIG_* default to on and allow it to be disabled with CONFIG_BASE_SMALL Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.