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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A59BC41514 for ; Mon, 29 Jul 2019 16:17:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1AED2067D for ; Mon, 29 Jul 2019 16:17:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387401AbfG2QR2 (ORCPT ); Mon, 29 Jul 2019 12:17:28 -0400 Received: from ale.deltatee.com ([207.54.116.67]:58892 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728367AbfG2QR2 (ORCPT ); Mon, 29 Jul 2019 12:17:28 -0400 Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.89) (envelope-from ) id 1hs8Ks-0001XX-8O; Mon, 29 Jul 2019 10:17:18 -0600 To: Sagi Grimberg , Stephen Bates , Hannes Reinecke , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Cc: Christoph Hellwig , Keith Busch , Jens Axboe , Chaitanya Kulkarni , Max Gurtovoy References: <20190725172335.6825-1-logang@deltatee.com> <1f202de3-1122-f4a3-debd-0d169f545047@suse.de> <8fd8813f-f8e1-2139-13bf-b0635a03bc30@deltatee.com> <175fa142-4815-ee48-82a4-18eb411db1ae@grimberg.me> <76f617b9-1137-48b6-f10d-bfb1be2301df@deltatee.com> <1260e01c-6731-52f7-ae83-0b90e0345c68@deltatee.com> <6DF00EEF-5A9D-49C9-A27C-BE34E594D9A9@raithlin.com> <322df1b1-dbba-2018-44da-c108336f8d55@grimberg.me> From: Logan Gunthorpe Message-ID: Date: Mon, 29 Jul 2019 10:17:10 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <322df1b1-dbba-2018-44da-c108336f8d55@grimberg.me> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: maxg@mellanox.com, Chaitanya.Kulkarni@wdc.com, axboe@fb.com, kbusch@kernel.org, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, hare@suse.de, sbates@raithlin.com, sagi@grimberg.me X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v6 00/16] nvmet: add target passthru commands support X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2019-07-29 10:15 a.m., Sagi Grimberg wrote: > >>> This is different from multipath on say a multi-controller PCI device >>> and trying to expose both those controllers through passthru. this is >>> where the problems we are discussing come up. >> >> I *think* there is some confusion. I *think* Sagi is talking about network multi-path (i.e. the ability for the host to connect to a controller on the target via two different network paths that fail-over as needed). I *think* Logan is talking about multi-port PCIe NVMe devices that allow namespaces to be accessed via more than one controller over PCIe (dual-port NVMe SSDs being the most obvious example of this today). > > Yes, I was referring to fabrics multipathing which is somewhat > orthogonal to the backend pci multipathing (unless I'm missing > something). Yes, so if we focus on the fabrics multipathing, the only issue I see is that only one controller can be connected to a passthru target (I believe this was at your request) so two paths simply cannot exist to begin with. I can easily remove that restriction. Logan