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 8B3F9C433EF for ; Tue, 12 Jul 2022 06:53:01 +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=DPKeMO/PaGNiIxRfoDr87m7kX3XO1hLM+sCkvnIZxbA=; b=CcvSPYM2OvU0r0Lr/sgBeRXXHD 6zn2VHtllHJNspJXca/wUWWWXS9Zc7QGR6lG/Ddwh04cPc9ClTSe1hh9vZxfQv9nHIg3ZarW9/VhT yY9tEgxY+M3MYY68DRL7TGOZWgT08B0I0UkvEvVX686M6bwElNKunJoXj1mNWxHFSwUiZAVR9Nu+x PxrYeXZCgvA4P/jwtyFkkxRWLiTwk0I8ppSeLsd0pNokqpu3/6WgDSbLNahHig3Oxp3ok4LAoCLJo uUkRYY0LxXtEMPtCZ4OaNPvbf+tYshW9nZRfXGYuvcGNCylLW5887sjNOKt/oKm1uy86sRZcnogxO cMoo4VMg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oB9lR-0089Bx-P4; Tue, 12 Jul 2022 06:52:57 +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 1oB9lP-00898u-2R for linux-nvme@lists.infradead.org; Tue, 12 Jul 2022 06:52:56 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 394AF68AA6; Tue, 12 Jul 2022 08:52:51 +0200 (CEST) Date: Tue, 12 Jul 2022 08:52:50 +0200 From: Christoph Hellwig To: Kanchan Joshi Cc: hch@lst.de, sagi@grimberg.me, 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: <20220712065250.GA6574@lst.de> References: <20220711110155.649153-1-joshi.k@samsung.com> <20220711110155.649153-5-joshi.k@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220711110155.649153-5-joshi.k@samsung.com> 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-20220711_235255_281716_93A67CBB X-CRM114-Status: UNSURE ( 9.19 ) X-CRM114-Notice: Please train this message. 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 Hmm, I'm a little confused on what this is trying to archive. The io_uring passthrough already does support multipathing, it picks an available path in nvme_ns_head_chr_uring_cmd and uses that. What this does is adding support for requeing on failure or the lack of an available path. Which very strongly is against our passthrough philosophy both in SCSI and NVMe where error handling is left entirely to the userspace program issuing the I/O. So this does radically change behavior in a very unexpected way. Why?