Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932142Ab3J1Q7h (ORCPT ); Mon, 28 Oct 2013 12:59:37 -0400 Received: from merlin.infradead.org ([205.233.59.134]:55198 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932104Ab3J1Q7g (ORCPT ); Mon, 28 Oct 2013 12:59:36 -0400 Message-ID: <526E97F4.3050104@kernel.dk> Date: Mon, 28 Oct 2013 10:59:32 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Christoph Hellwig CC: Alexander Gordeev , Tejun Heo , Nicholas Bellinger , linux-kernel@vger.kernel.org Subject: Re: blk-mq flush fix References: <20131026114612.GA8576@infradead.org> <20131026153124.GA22227@infradead.org> <20131027222914.GG22549@kernel.dk> <20131028084821.GA31270@infradead.org> <526E90D7.1070604@kernel.dk> <20131028164641.GA1046@infradead.org> In-Reply-To: <20131028164641.GA1046@infradead.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1195 Lines: 27 On 10/28/2013 10:46 AM, Christoph Hellwig wrote: > On Mon, Oct 28, 2013 at 10:29:11AM -0600, Jens Axboe wrote: >> It's not that I think the existing patch is THAT bad, it fits in alright >> with the reserved tagging and works regardless of whether a driver uses >> reserved tags or not. And it does have the upside of not requiring >> special checks or logic for this special non-tagged request that using >> the preallocated would might need. > > The problem with it is that it will pass a tag number to the low level > driver which it doesn't expect. In case the tags are used 1:1 as > hardware tags that would lead to nasy bugs. > > At vefy least we'd need to mess with ->tag for this special request. Yes indeed. Actually the more I think about it, the better I like just using the normal tagging infrastructure and punting to a reserved tag for the flush. Just needs adding of the check whether it actually needs it or not. -- 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/