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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F3071C433EF for ; Wed, 13 Jul 2022 05:36:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=8F9asmchbHoMtKx4dWhxDQzOKwtT1HulJnrCajrND54=; b=0twkVxaHmjxfp3aEY1Or4Yi1gL 56gN8+BXklX0VYFK9OUwRcDekyoYq5wITar0AZyRTwfPe9Jt3sR44hOoYs2SGyf9Ml00NTrsS2jvZ 1mchL98aJgjpHiQrRTH6uAwwKZ+j/ujSVguh+WKE50qXDEVI6SujSsDyqnt2Q1zgXJIvixVsKerq2 9/9tFQmAag2MgyWdqKzyxvtayR98HLn9RuGKIwDO3UwE54UZvxE4JRlh4Izt2/wBiAQky9nlDXrmm rhZVs0wiW5yZ9Bg6jHv9xGHkTY8Ou84HaYqWxxdGJel5XhF6rd1GQIco/Xkq/9la2No+Q8gYp1cSb LiP6INMw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oBV3K-000Hmp-Oq; Wed, 13 Jul 2022 05:36:50 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oBV3H-000HjF-Lp for linux-nvme@lists.infradead.org; Wed, 13 Jul 2022 05:36:49 +0000 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) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220712_223647_904534_BDE0D8FD X-CRM114-Status: GOOD ( 15.93 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.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.