Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756464Ab1BXQsE (ORCPT ); Thu, 24 Feb 2011 11:48:04 -0500 Received: from cantor.suse.de ([195.135.220.2]:53409 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756378Ab1BXQsA (ORCPT ); Thu, 24 Feb 2011 11:48:00 -0500 Date: Thu, 24 Feb 2011 17:47:58 +0100 From: Jan Kara To: Chris Mason Cc: Joel Becker , "Martin K. Petersen" , djwong , Jens Axboe , linux-kernel , linux-fsdevel , Mingming Cao , linux-scsi Subject: Re: [RFC] block integrity: Fix write after checksum calculation problem Message-ID: <20110224164758.GH23042@quack.suse.cz> References: <20110222020022.GH32261@tux1.beaverton.ibm.com> <20110223202446.GG4020@noexit> <1298493173-sup-8301@think> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1298493173-sup-8301@think> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1618 Lines: 35 On Wed 23-02-11 15:35:11, Chris Mason wrote: > Excerpts from Joel Becker's message of 2011-02-23 15:24:47 -0500: > > On Tue, Feb 22, 2011 at 11:45:44AM -0500, Martin K. Petersen wrote: > > > Also, DIX is only the tip of the iceberg. Many other impending > > > technologies feature checksums and require pages to be stable during I/O > > > due to checksumming, encryption and so on. > > > > > > The VM is already trying to do the right thing. We just need the > > > relevant filesystems to catch up. > > > > ocfs2 handles stable metadata for its checksums when feeding > > things to the journal. If we're doing pagecache-based I/O, is the > > pagecache going to help here for data? > > Data is much easier than metadata. All you really need is to wait on > writeback in file_write, wait on writeback in page_mkwrite, and make > sure you don't free blocks back to the allocator that are actively under > IO. > > I expect the hard part to be jbd and metadata in ext34. But JBD already has to do data copy if a buffer is going to be modified before/while it is written to the journal. So we should alredy do all that is needed for metadata. I don't say there aren't any bugs as they could be triggered only by crashing at the wrong moment and observing fs corruption. But most of the work should be there... Honza -- Jan Kara SUSE Labs, CR -- 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/