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 15EF8C43334 for ; Tue, 12 Jul 2022 06:52:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232191AbiGLGw4 (ORCPT ); Tue, 12 Jul 2022 02:52:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231564AbiGLGwz (ORCPT ); Tue, 12 Jul 2022 02:52:55 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5B4D8AEC2; Mon, 11 Jul 2022 23:52:54 -0700 (PDT) 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) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.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?