From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755263AbXD0EG7 (ORCPT ); Fri, 27 Apr 2007 00:06:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755267AbXD0EG7 (ORCPT ); Fri, 27 Apr 2007 00:06:59 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:54740 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755263AbXD0EG5 (ORCPT ); Fri, 27 Apr 2007 00:06:57 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Jens Axboe Cc: Christoph Lameter , Christoph Hellwig , Nick Piggin , David Chinner , linux-kernel@vger.kernel.org, Mel Gorman , William Lee Irwin III , Badari Pulavarty , Maxim Levitsky Subject: Re: [00/17] Large Blocksize Support V3 References: <20070426180358.GG2017@kernel.dk> <20070426180932.GA10642@infradead.org> <20070426181249.GH2017@kernel.dk> <20070426182945.GJ2017@kernel.dk> <20070426183935.GK2017@kernel.dk> <20070426194234.GL2017@kernel.dk> Date: Thu, 26 Apr 2007 22:05:43 -0600 In-Reply-To: <20070426194234.GL2017@kernel.dk> (Jens Axboe's message of "Thu, 26 Apr 2007 21:42:36 +0200") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > On Thu, Apr 26 2007, Eric W. Biederman wrote: > > Yep, if you could just have > PAGE_CACHE_SIZE blocks in the filesystem > easily, the problem would basically be solved for cd and dvd packet > writing. Ok. I'm not in a position to do this work. But I will keep it in mind and look at it. >> Am I correct in assuming that the problem is primarily about getting >> filesystems (and other upper layers) to submit BIOs that take into >> consideration the larger block size of the underlying device, so >> that read/modify write is not needed in the pktcdvd layer? > > Yes, that is exactly the problem. Once you have that, pktcdvd is pretty > much reduced to setup and init code, the actual data handling can be > done by sr or ide-cd directly. You could merge it into cdrom.c, it would > not be very different from mt-rainier handling (which basically does RMW > in firmware, so it works for any write, but performance is of course > horrible if you don't do it right). Thanks for the clarification. So we do have a clear problem that we do not have generic support for large sector sizes residing in the page cache. There is one place where this is a direct effect fs/block_dev.c We have an indirect affect in the filesystems because there a few bits of generic support missing and there is no linux convention on how to handle this case. I expect if we can enhance fs/block_dev.c to handle this case the other parts will fall out naturally. Eric