Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754576AbXJVTjx (ORCPT ); Mon, 22 Oct 2007 15:39:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752556AbXJVTjp (ORCPT ); Mon, 22 Oct 2007 15:39:45 -0400 Received: from hoboe1bl1.telenet-ops.be ([195.130.137.72]:48921 "EHLO hoboe1bl1.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752304AbXJVTjo (ORCPT ); Mon, 22 Oct 2007 15:39:44 -0400 Date: Mon, 22 Oct 2007 21:39:39 +0200 (CEST) From: Geert Uytterhoeven To: Jens Axboe Cc: Linus Torvalds , Linux Kernel Development , mingo@elte.hu, Linux/m68k Subject: Re: [PATCH 09/10] Change table chaining layout In-Reply-To: <1193076664-13652-10-git-send-email-jens.axboe@oracle.com> Message-ID: References: <1193076664-13652-1-git-send-email-jens.axboe@oracle.com> <1193076664-13652-10-git-send-email-jens.axboe@oracle.com> 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 Content-Length: 1212 Lines: 32 On Mon, 22 Oct 2007, Jens Axboe wrote: > Change the page member of the scatterlist structure to be an unsigned > long, and encode more stuff in the lower bits: > > - Bits 0 and 1 zero: this is a normal sg entry. Next sg entry is located > at sg + 1. > - Bit 0 set: this is a chain entry, the next real entry is at ->page_link > with the two low bits masked off. > - Bit 1 set: this is the final entry in the sg entry. sg_next() will return > NULL when passed such an entry. Better safe than sorry... Is it possible that a chain entry pointer has bit 1 set on architectures (e.g. m68k) where the natural alignment of 32-bit quantities is _2_ bytes, not 4? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds - 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/