Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932471AbWESThN (ORCPT ); Fri, 19 May 2006 15:37:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932475AbWESThN (ORCPT ); Fri, 19 May 2006 15:37:13 -0400 Received: from mx1.redhat.com ([66.187.233.31]:35044 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S932471AbWESThL (ORCPT ); Fri, 19 May 2006 15:37:11 -0400 Subject: Re: [PATCH] sector_t overflow in block layer From: "Stephen C. Tweedie" To: Andreas Dilger Cc: Linus Torvalds , Anton Altaparmakov , "ext2-devel@lists.sourceforge.net" , Andrew Morton , linux-kernel , Stephen Tweedie In-Reply-To: <20060518232324.GW5964@schatzie.adilger.int> References: <1147884610.16827.44.camel@localhost.localdomain> <1147888715.12067.38.camel@dyn9047017100.beaverton.ibm.com> <20060517235804.GA5731@schatzie.adilger.int> <1147947803.5464.19.camel@sisko.sctweedie.blueyonder.co.uk> <20060518185955.GK5964@schatzie.adilger.int> <20060518232324.GW5964@schatzie.adilger.int> Content-Type: text/plain Date: Fri, 19 May 2006 20:36:52 +0100 Message-Id: <1148067412.5156.65.camel@sisko.sctweedie.blueyonder.co.uk> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-27) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1360 Lines: 32 Hi, On Thu, 2006-05-18 at 17:23 -0600, Andreas Dilger wrote: > I looked at that also, but it isn't clear from the use of "b_size" here > that there is any constraint that b_size is a power of two, only that it > is a multiple of 512. Granted, I don't know whether there are any users > of such a crazy thing, but the fact that this is in bytes instead of a > shift made me think twice. Yeah. It was very strongly constrained to a power-of-two in the dim and distant past, when buffer_heads were only ever used for true buffer- cache data (the entire IO path had to be special-cased for IO that wasn't from the buffer cache, such as swap IO.) But more recently it has been a lot more relaxed, and we've had patches like Jens' "varyIO" patches on 2.4 which routinely generated odd-sized b_size buffer_heads when doing raw/direct IO on unaligned disk offsets. But in 2.6, I _think_ such paths should be going straight to bio, not via submit_bh. Direct IO certainly doesn't use bh's any more, and pretty much any other normal disk IO paths are page-aligned. I might be missing something, though. --Stephen - 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/