From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751653Ab1DCWK5 (ORCPT ); Sun, 3 Apr 2011 18:10:57 -0400 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:33892 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750936Ab1DCWK4 (ORCPT ); Sun, 3 Apr 2011 18:10:56 -0400 Message-ID: <4D98F061.5030003@kernel.dk> Date: Mon, 04 Apr 2011 00:10:41 +0200 From: Jens Axboe MIME-Version: 1.0 To: Konstantin Khlebnikov CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] block: fix request sorting at unplug References: <20110402153737.15555.75762.stgit@localhost6> In-Reply-To: <20110402153737.15555.75762.stgit@localhost6> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-04-02 17:37, Konstantin Khlebnikov wrote: > Comparison function for list_sort() must be anticommutative, > otherwise it is not sorting in ordinary meaning. > > But fortunately list_sort() always check ((*cmp)(priv, a, b) <= 0) > it not distinguish negative and zero, so comparison function can > implement only less-or-equal instead of full three-way comparison. Thanks, good catch! It's an optimization, so no breakage. But if you end up often having > 1 queue plugged, it's a good optimization. -- Jens Axboe