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=-2.2 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 3B844C76190 for ; Thu, 25 Jul 2019 18:36:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 205E2229F9 for ; Thu, 25 Jul 2019 18:36:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726158AbfGYSgl (ORCPT ); Thu, 25 Jul 2019 14:36:41 -0400 Received: from ale.deltatee.com ([207.54.116.67]:41400 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726107AbfGYSgl (ORCPT ); Thu, 25 Jul 2019 14:36:41 -0400 Received: from s01061831bf6ec98c.cg.shawcable.net ([68.147.80.180] helo=[192.168.6.132]) by ale.deltatee.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1hqibL-0002j4-4Y; Thu, 25 Jul 2019 12:36:28 -0600 To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig , Sagi Grimberg , Keith Busch , Jens Axboe , Chaitanya Kulkarni , Max Gurtovoy , Stephen Bates , Alexander Viro References: <20190725172335.6825-1-logang@deltatee.com> <20190725172335.6825-3-logang@deltatee.com> <20190725174032.GA27818@kroah.com> <682ff89f-04e0-7a94-5aeb-895ac65ee7c9@deltatee.com> <20190725180816.GA32305@kroah.com> <20190725182701.GA11547@kroah.com> From: Logan Gunthorpe Message-ID: Date: Thu, 25 Jul 2019 12:36:24 -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: <20190725182701.GA11547@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 68.147.80.180 X-SA-Exim-Rcpt-To: viro@zeniv.linux.org.uk, sbates@raithlin.com, maxg@mellanox.com, Chaitanya.Kulkarni@wdc.com, axboe@fb.com, kbusch@kernel.org, sagi@grimberg.me, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path() 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-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2019-07-25 12:27 p.m., Greg Kroah-Hartman wrote: >>> Why do you have a "string" within the kernel and are not using the >>> normal open() call from userspace on the character device node on the >>> filesystem in your namespace/mount/whatever? >> >> NVMe-OF is configured using configfs. The target is specified by the >> user writing a path to a configfs attribute. This is the way it works >> today but with blkdev_get_by_path()[1]. For the passthru code, we need >> to get a nvme_ctrl instead of a block_device, but the principal is the same. > > Why isn't a fd being passed in there instead of a random string? I wouldn't know the answer to this but I assume because once we decided to use configfs, there was no way for the user to pass the kernel an fd. > Seems odd, but oh well, that ship sailed a long time ago for block > devices I guess. Yup. > So what do you actually _do_ with that char device once you have it? We lookup the struct nvme_ctrl and use it to submit passed-through NVMe commands directly to the controller. Logan