Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932177AbWESKBr (ORCPT ); Fri, 19 May 2006 06:01:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932238AbWESKBr (ORCPT ); Fri, 19 May 2006 06:01:47 -0400 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:32654 "EHLO ecfrec.frec.bull.fr") by vger.kernel.org with ESMTP id S932177AbWESKBp (ORCPT ); Fri, 19 May 2006 06:01:45 -0400 Message-ID: <446D977B.3030809@bull.net> Date: Fri, 19 May 2006 12:01:31 +0200 From: Zoltan Menyhart User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913 X-Accept-Language: en-us, en, fr, hu MIME-Version: 1.0 To: "Stephen C. Tweedie" , Jan Kara Cc: linux-kernel Subject: Re: [PATCH] Change ll_rw_block() calls in JBD References: <446C2F89.5020300@bull.net> <20060518134533.GA20159@atrey.karlin.mff.cuni.cz> <446C8EB1.3090905@bull.net> <1147991117.5464.124.camel@sisko.sctweedie.blueyonder.co.uk> In-Reply-To: <1147991117.5464.124.camel@sisko.sctweedie.blueyonder.co.uk> X-MIMETrack: Itemize by SMTP Server on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 19/05/2006 12:04:50, Serialize by Router on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 19/05/2006 12:04:56, Serialize complete at 19/05/2006 12:04:56 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1491 Lines: 40 I'd like to take this opportunity to ask some questions I always wanted to ask about committing a transaction(*) but were afraid to ask :-) We wait for several types of I/O-s: - "Wait for all previously submitted IO to complete" (t_sync_datalist) - wait_for_iobuf: (t_buffers) - wait_for_ctlbuf: (t_log_list) before "journal_write_commit_record()" gets invoked. Why do not we wait for them at the very last moment in batch, is it important that e.g. all the buffers from "t_buffers" be completed before we start with the ones on "t_log_list"? If "JFS_BARRIER" is set, why do we wait for these I/O-s at all? (The "ordered" attribute is set => all the previous I/O-s must have hit the permanent storage before the commit record can do.) Why do we let the EXT3 layer to decide, why do not we ask the "bio" if the "ordered" attribute is supported and use it systematically? There is a comment in "journal_write_commit_record()": /* is it possible for another commit to fail at roughly * the same time as this one?... Another commit for the same journal? (If not the same journal, why is it a problem?) If a barrier-based sync has failed on a device, does the actual I/O start by itself (not caring for the ordering issue)? Thanks, Zoltan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/