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 D384BC43334 for ; Wed, 13 Jul 2022 11:28:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231272AbiGML24 (ORCPT ); Wed, 13 Jul 2022 07:28:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52336 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235465AbiGML2y (ORCPT ); Wed, 13 Jul 2022 07:28:54 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29C9E29CAF; Wed, 13 Jul 2022 04:28:49 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id 3B61267373; Wed, 13 Jul 2022 13:28:46 +0200 (CEST) Date: Wed, 13 Jul 2022 13:28:45 +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: <20220713112845.GA780@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> <20220713101235.GA27815@lst.de> <772b461a-bc43-c229-906d-0e280091e17f@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <772b461a-bc43-c229-906d-0e280091e17f@grimberg.me> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Jul 13, 2022 at 02:00:56PM +0300, Sagi Grimberg wrote: > I view uring passthru somewhat as a different thing than sending SG_IO > ioctls to dm-mpath. But it can be argued otherwise. > > BTW, the only consumer of it that I'm aware of commented that he > expects dm-mpath to retry SG_IO when dm-mpath retry for SG_IO submission > was attempted (https://www.spinics.net/lists/dm-devel/msg46924.html). Yeah. But the point is that if we have a path failure, the kernel will pick a new path next time anyway, both in dm-mpath and nvme-mpath. > I still think that there is a problem with the existing semantics for > passthru requests over mpath device nodes. > > Again, I think it will actually be cleaner not to expose passthru > devices for mpath at all if we are not going to support retry/failover. I think they are very useful here. Users of passthrough interface need to be able to retry anyway, even on non-multipath setups. And a dumb retry will do the right thing.