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 20C6BC433EF for ; Wed, 13 Jul 2022 05:41:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233681AbiGMFlx (ORCPT ); Wed, 13 Jul 2022 01:41:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233952AbiGMFlb (ORCPT ); Wed, 13 Jul 2022 01:41:31 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0AB7E026F; Tue, 12 Jul 2022 22:36:38 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id 82B0E68AA6; Wed, 13 Jul 2022 07:36:33 +0200 (CEST) Date: Wed, 13 Jul 2022 07:36:33 +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: <20220713053633.GA13135@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <436c8875-5a99-4328-80ac-6a5aef7f16f4@grimberg.me> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Jul 12, 2022 at 11:13:57PM +0300, Sagi Grimberg wrote: > I think the difference from scsi-generic and controller nvme passthru is > that this is a mpath device node (or mpath chardev). This is why I think > that users would expect that it would have equivalent multipath > capabilities (i.e. failover). How is that different from /dev/sg? > In general, I think that uring passthru as an alternative I/O interface > and as such needs to be able to failover. If this is not expected from > the interface, then why are we exposing a chardev for the mpath device > node? why not only the bottom namespaces? The failover will happen when you retry, but we leave that retry to userspace. There even is the uevent to tell userspace when a new path is up.