From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753435Ab1G3HV0 (ORCPT ); Sat, 30 Jul 2011 03:21:26 -0400 Received: from oproxy3-pub.bluehost.com ([69.89.21.8]:55896 "HELO oproxy3-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752715Ab1G3HVY (ORCPT ); Sat, 30 Jul 2011 03:21:24 -0400 Message-ID: <4E33B1EC.9030004@gmail.com> Date: Sat, 30 Jul 2011 15:25:32 +0800 From: Coly Li Reply-To: colyli@gmail.com User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.13) Gecko/20101206 SUSE/3.1.7 Thunderbird/3.1.7 MIME-Version: 1.0 To: Andreas Dilger , "Darrick J. Wong" , Andreas Dilger , Mingming Cao , "Theodore Ts'o" , linux-ext4 , linux-kernel Subject: Re: [PATCH 0/2] Add inode checksum support to ext4 References: <20110406224410.GB24354@tux1.beaverton.ibm.com> <1302290868.4461.7.camel@mingming-laptop> <20110727082730.GG20655@tux1.beaverton.ibm.com> <20110728165615.GI20655@tux1.beaverton.ibm.com> <20110728220735.GA27253@noexit.corp.google.com> <0E795C1D-AD1E-4CC4-9426-2B58D98B14DC@dilger.ca> <20110729131937.GB5910@noexit.corp.google.com> In-Reply-To: <20110729131937.GB5910@noexit.corp.google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Identified-User: {1390:box585.bluehost.com:colyli:coly.li} {sentby:smtp auth 123.122.104.166 authed with i@coly.li} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011年07月29日 21:19, Joel Becker Wrote: > On Fri, Jul 29, 2011 at 03:48:45AM -0600, Andreas Dilger wrote: >> On 2011-07-28, at 4:07 PM, Joel Becker wrote: >>> We use ethernet crc32 in ocfs2. btrfs uses crc32c. Frankly, I >>> could have used crc32c if I'd really thought about the hardware >>> acceleration benefits. I think it's a good idea for ext4. >> >> The problem with crc32[c] is that if you don't have hardware acceleration >> it is terribly slow. > > We find ethernet crc32 just fine in ocfs2. I use the kernel's > implementation, which survives everyone's network traffic, and of course > we added the triggers to jbd2 so we only have to do the calculations on > read and write. > Ext4 supports non-journal mode, and there are a few users (Google, Taobao, etc.). A trigger of jbd2 may not work well for non-journal Ext4 ... And in non-journal mode, there is not copy of any meta data block in jbd2, we need to be more careful in check summing, e.g. inode/block bitmap blocks... >> Yes, it makes sense to just put a "fake" dirent at the end of the leaf block, >> or similar. I don't think it is necessary to modify existing directories or >> extent blocks to add these structures in, if there is no room, but for new >> blocks, or blocks with space it is enough. > > We have tunefs.ocfs2 code to adjust existing directories to add > the trailer. It's not too bad, really. Agree, enable/disable the trailer isn't that difficult. We need more eyes to take care the user space tools. Coly