Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761523AbXJQSWY (ORCPT ); Wed, 17 Oct 2007 14:22:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757346AbXJQSWO (ORCPT ); Wed, 17 Oct 2007 14:22:14 -0400 Received: from brick.kernel.dk ([87.55.233.238]:2871 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757685AbXJQSWN (ORCPT ); Wed, 17 Oct 2007 14:22:13 -0400 Date: Wed, 17 Oct 2007 20:22:07 +0200 From: Jens Axboe To: Linus Torvalds Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [bug] block subsystem related crash with latest -git Message-ID: <20071017182206.GS15552@kernel.dk> References: <20071017154655.GA13394@elte.hu> <20071017165949.GF15552@kernel.dk> <20071017170804.GG15552@kernel.dk> <20071017180042.GP15552@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1311 Lines: 38 On Wed, Oct 17 2007, Linus Torvalds wrote: > > > On Wed, 17 Oct 2007, Jens Axboe wrote: > > > > > > So avoiding the "sg_next()" on the last entry is pointless. > > > > Yeah, I didn't quite understand why if sg was valid, why dereferencing > > *(sg + 1)->page would crap out :/ > > Actually, I take that back. If 'sg' is the last entry in a *non*linked > scatter-gather list (ie we don't use the last entry as a link, we actually > use it as a real SG entry), then "sg_next(sg)" will indeed access past the > end of the whole allocated array, and will access one past the end. > > And with page-alloc debugging, that *will* blow up. > > So I think your change to use "sg_next()" only when you actually need a > next pointer is the correct one after all. Thanks, so I'm not totally crazy :-) Can you just pull: git://git.kernel.dk/data/git/linux-2.6-block.git for-linus then so we get those two pieces correct? Then the remaining issue seems to be a new one that is biting Ingo elsewhere, at least we'll all be on the same page then. -- Jens Axboe - 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/