From: Jan Kara Subject: Re: Delayed allocation and page_lock vs transaction start ordering Date: Mon, 21 Apr 2008 19:13:12 +0200 Message-ID: <20080421171312.GJ6119@duck.suse.cz> References: <20080415161430.GC28699@duck.suse.cz> <1208282932.3636.9.camel@localhost.localdomain> <20080416093803.GB6116@duck.suse.cz> <20080418185447.GA3424@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mingming Cao , linux-ext4@vger.kernel.org, sandeen@redhat.com To: Andreas Dilger Return-path: Received: from styx.suse.cz ([82.119.242.94]:36247 "EHLO mail.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755070AbYDURNO (ORCPT ); Mon, 21 Apr 2008 13:13:14 -0400 Content-Disposition: inline In-Reply-To: <20080418185447.GA3424@webber.adilger.int> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri 18-04-08 12:54:47, Andreas Dilger wrote: > On Apr 16, 2008 11:38 +0200, Jan Kara wrote: > > On Tue 15-04-08 11:08:52, Mingming Cao wrote: > > > I guess this reserve locking ordering allows support writepages() for > > > ext3/4? What other the benefits? > > > > Yes, that is one advantage. The other one (which I care about the most) > > is that transaction commit code can take page_lock in the new locking order > > which is necessary for the new ordered mode rewrite. > > My understanding is that the main reason for the ordered mode rewrite is > specifically to allow delalloc to still support ordered mode semantics. > If the lock ordering is changed, and the jbd ordered mode is changed, but > we don't support that with delalloc then we will have made a lot of changes > (and likely introduced some bugs) with little benefit. Yes, with ordered mode rewrite, handling of data=ordered,delalloc is going to be much simpler. But not that it would be my main motivation... Honza -- Jan Kara SUSE Labs, CR