From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754499AbYCHMOd (ORCPT ); Sat, 8 Mar 2008 07:14:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751367AbYCHMOX (ORCPT ); Sat, 8 Mar 2008 07:14:23 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34561 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751065AbYCHMOW (ORCPT ); Sat, 8 Mar 2008 07:14:22 -0500 Date: Sat, 8 Mar 2008 07:14:20 -0500 From: Christoph Hellwig To: Andreas Dilger Cc: Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] JBD ordered mode rewrite Message-ID: <20080308121420.GA17812@infradead.org> References: <20080306174209.GA14193@duck.suse.cz> <20080307235210.GM1881@webber.adilger.int> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080307235210.GM1881@webber.adilger.int> User-Agent: Mutt/1.5.17 (2007-11-01) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 07, 2008 at 04:52:10PM -0700, Andreas Dilger wrote: > I'm looking at what implications this has for delayed allocation in ext4, > because the vast majority of file data will be unmapped in that case > and a journal commit in ordered mode will no longer cause the data to > be flushed to disk. The buffers shouldn't be unmapped. They are accounted for and doing the delalloc conversion is easier than really allocating blocks for truely unmapped blocks. You should probably reuse BH_Delay for that as it has all the right handling in buffer.c in place due to XFS. Also on any filesystem with ->page_mkwrite implemented unmapped buffers should be entirely gone because we now have the proper early reservation / allocation infrastructure in place.