Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751352AbWCBCXF (ORCPT ); Wed, 1 Mar 2006 21:23:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751393AbWCBCXE (ORCPT ); Wed, 1 Mar 2006 21:23:04 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:56264 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1751352AbWCBCXD (ORCPT ); Wed, 1 Mar 2006 21:23:03 -0500 Date: Thu, 2 Mar 2006 13:22:32 +1100 From: Nathan Scott To: Andrew Morton Cc: Badari Pulavarty , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] change buffer_head.b_size to size_t Message-ID: <20060302132232.C88229@wobbly.melbourne.sgi.com> References: <1141075239.10542.19.camel@dyn9047017100.beaverton.ibm.com> <1141075361.10542.21.camel@dyn9047017100.beaverton.ibm.com> <20060301175148.2250b36e.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20060301175148.2250b36e.akpm@osdl.org>; from akpm@osdl.org on Wed, Mar 01, 2006 at 05:51:48PM -0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1389 Lines: 35 On Wed, Mar 01, 2006 at 05:51:48PM -0800, Andrew Morton wrote: > Badari Pulavarty wrote: > > > > + * Historically, a buffer_head was used to map a single block > > + * within a page, and of course as the unit of I/O through the > > + * filesystem and block layers. Nowadays the basic I/O unit > > + * is the bio, and buffer_heads are used for extracting block > > + * mappings (via a get_block_t call), for tracking state within > > + * a page (via a page_mapping) and for wrapping bio submission > > + * for backward compatibility reasons (e.g. submit_bh). > > Well kinda. A buffer_head remains the kernel's basic abstraction for a > "disk block". Thats what I said (meant to say) with "buffer_heads are used for extracting block mappings". I think by "disk block" you mean what I'm thinking of as a "block mapping" (series of contiguous blocks). I'd think of a sector_t as a "disk block", but maybe I'm just wierd that way... a better wordsmith should jump in and update the comment I guess. > We cannot replace that with `struct page' (size isn't > flexible) nor of course with `struct bio'. Indeed. -- Nathan - 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/