From: Alex Tomas Subject: Re: booked-page-flag.patch Date: Fri, 16 Feb 2007 10:30:39 +0300 Message-ID: References: <20070215004504.023a90f0.akpm@linux-foundation.org> <45D495EA.3060200@redhat.com> <20070215125654.b0f18ab3.akpm@linux-foundation.org> <20070215152352.6ddcfa92.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Alex Tomas , Eric Sandeen , "Theodore Ts'o" , "linux-ext4@vger.kernel.org" To: Andrew Morton Return-path: Received: from [80.71.245.246] ([80.71.245.246]:52090 "EHLO nsold.rialcom.ru" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S932589AbXBPHak (ORCPT ); Fri, 16 Feb 2007 02:30:40 -0500 In-Reply-To: <20070215152352.6ddcfa92.akpm@linux-foundation.org> (Andrew Morton's message of "Thu\, 15 Feb 2007 15\:23\:52 -0800") Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org >>>>> Andrew Morton (AM) writes: -> get_block(with BH_Delay) can be used to signal >> filesystem that no actual allocation is required. >> so, aware filesystem can just reserve space. then -> writepages() should walk through the pages like >> it does currently, collect contiugous sequences >> and again call ->get_block(w/o BH_Delay) with b_size >> covering all contiguous pages ... >> AM> That sounds like it'd work, yes. AM> Except for an address_space which is using delayed allocation, its -> prepare_write wouldn't call get_block at all, so perhaps that isn't AM> needed. hmm. I thought it has to call get_block() at least to know whether the block is already allocated. and I was going to reserve space in prepare_write for which some fs-specific method is needed becase only fs knows how much metadata it'd need. thanks, Alex