From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752252AbaBGOTS (ORCPT ); Fri, 7 Feb 2014 09:19:18 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:33916 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751463AbaBGOTQ (ORCPT ); Fri, 7 Feb 2014 09:19:16 -0500 Date: Fri, 7 Feb 2014 06:19:15 -0800 From: Christoph Hellwig To: Shaohua Li Cc: Christoph Hellwig , Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] block: rework flush sequencing for blk-mq Message-ID: <20140207141915.GA24176@infradead.org> References: <20140130132620.GA6031@infradead.org> <20140130132630.GB6031@infradead.org> <20140207011827.GA4735@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140207011827.GA4735@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 07, 2014 at 09:18:27AM +0800, Shaohua Li wrote: > Reusing the tag for flush request is considered before. The problem is driver > need get a request from a tag, reusing tag breaks this. The possible solution > is we provide a blk_mq_tag_to_request, and force driver uses it. And in this > function, if tag equals to flush_rq tag, we return flush_request. If we want to support tag to request reverse mapping we defintively need to do this in the core, at which point special casing flush_rq there is easy. Which driver needs the reverse mapping? Neither virtio_blk nor null_blk seem to and I've not seen any other conversions submitted except for the scsi work.