From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754149AbYKJFab (ORCPT ); Mon, 10 Nov 2008 00:30:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751757AbYKJFaV (ORCPT ); Mon, 10 Nov 2008 00:30:21 -0500 Received: from hera.kernel.org ([140.211.167.34]:46783 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbYKJFaT (ORCPT ); Mon, 10 Nov 2008 00:30:19 -0500 Message-ID: <4917C6DD.4010500@kernel.org> Date: Mon, 10 Nov 2008 14:30:05 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.17 (X11/20080922) MIME-Version: 1.0 To: Jens Axboe , Jeff Garzik , Linus Torvalds , IDE/ATA development list , Linux Kernel Subject: Re: request to revert libata-convert-to-block-tagging patches References: <4917C449.2080504@kernel.org> In-Reply-To: <4917C449.2080504@kernel.org> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Mon, 10 Nov 2008 05:30:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tejun Heo wrote: > #1 is easy to fix but #2 requires either adding a spinlock or two atomic > variables to struct blk_queue_tag to keep the current behavior while > guaranteeing that tags are used in order. Also, there's delay between > libata marks a request complete and the request actually gets completed > and the tag is freed. If another request gets issued inbetween, the tag > number can't be guaranteed. This can be worked around by re-mapping tag > number in libata depending on command type but, well then, it's worse > than the original implementation. I think this can be made to work by making tag free synchronous (ie. doing it when the request is passed over to softirq) but I don't think things like that should go into 2.6.28 at this point. Thanks. -- tejun