From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17637C433EF for ; Wed, 13 Jul 2022 10:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234394AbiGMKMl (ORCPT ); Wed, 13 Jul 2022 06:12:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231969AbiGMKMk (ORCPT ); Wed, 13 Jul 2022 06:12:40 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E1A6F789B; Wed, 13 Jul 2022 03:12:39 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id 7CBD167373; Wed, 13 Jul 2022 12:12:35 +0200 (CEST) Date: Wed, 13 Jul 2022 12:12:35 +0200 From: Christoph Hellwig To: Sagi Grimberg Cc: Christoph Hellwig , Kanchan Joshi , kbusch@kernel.org, axboe@kernel.dk, io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, asml.silence@gmail.com, joshiiitr@gmail.com, anuj20.g@samsung.com, gost.dev@samsung.com Subject: Re: [PATCH for-next 4/4] nvme-multipath: add multipathing for uring-passthrough commands Message-ID: <20220713101235.GA27815@lst.de> References: <20220711110155.649153-1-joshi.k@samsung.com> <20220711110155.649153-5-joshi.k@samsung.com> <20220712065250.GA6574@lst.de> <436c8875-5a99-4328-80ac-6a5aef7f16f4@grimberg.me> <20220713053633.GA13135@lst.de> <24f0a3e6-aa53-8c69-71b7-d66289a63eae@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <24f0a3e6-aa53-8c69-71b7-d66289a63eae@grimberg.me> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Jul 13, 2022 at 11:04:31AM +0300, Sagi Grimberg wrote: > Maybe the solution is to just not expose a /dev/ng for the mpath device > node, but only for bottom namespaces. Then it would be completely > equivalent to scsi-generic devices. > > It just creates an unexpected mix of semantics of best-effort > multipathing with just path selection, but no requeue/failover... Which is exactly the same semanics as SG_IO on the dm-mpath nodes. > If the user needs to do the retry, discover and understand namespace > paths, ANA states, controller states, etc. Why does the user need a > mpath chardev at all? The user needs to do that for all kinds of other resons anyway, as we don't do any retries for passthrough at all.