Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757636AbXEPNVD (ORCPT ); Wed, 16 May 2007 09:21:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754130AbXEPNUy (ORCPT ); Wed, 16 May 2007 09:20:54 -0400 Received: from mx1.redhat.com ([66.187.233.31]:57178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751581AbXEPNUx (ORCPT ); Wed, 16 May 2007 09:20:53 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <464AF224.30105@yahoo.com.au> References: <464AF224.30105@yahoo.com.au> <20070318233008.GA32597093@melbourne.sgi.com> <18993.1179310769@redhat.com> To: Nick Piggin Cc: David Chinner , lkml , linux-mm , linux-fsdevel Subject: Re: [PATCH 1 of 2] block_page_mkwrite() Implementation V2 X-Mailer: MH-E 8.0; nmh 1.1; GNU Emacs 22.0.50 Date: Wed, 16 May 2007 14:20:47 +0100 Message-ID: <17244.1179321647@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1226 Lines: 27 Nick Piggin wrote: > Dave is using prepare_write here to ensure blocks are allocated in the > given range. The filesystem's ->nopage function must ensure it is uptodate > before allowing it to be mapped. Which is fine... assuming it's called. For blockdev-based filesystems, this is probably true. But I'm not sure you can guarantee it. I've seen Ext3, for example, unlocking a page that isn't yet uptodate. nopage() won't get called on it again, but prepare_write() might. I don't know why this happens, but it's something I've fallen over in doing CacheFiles. When reading, readpage() is just called on it again and again until it is up to date. When writing, prepare_write() is called correctly. > Consider that the code currently works OK today _without_ page_mkwrite. > page_mkwrite is being added to do block allocation / reservation. Which doesn't prove anything. All it means is that PG_uptodate being unset is handled elsewhere. David - 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/