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 DB761C76194 for ; Thu, 25 Jul 2019 19:41:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C12552238C for ; Thu, 25 Jul 2019 19:41:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726265AbfGYTla (ORCPT ); Thu, 25 Jul 2019 15:41:30 -0400 Received: from ale.deltatee.com ([207.54.116.67]:42782 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726230AbfGYTla (ORCPT ); Thu, 25 Jul 2019 15:41:30 -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 1hqjc6-0004BV-00; Thu, 25 Jul 2019 13:41:18 -0600 To: Greg Kroah-Hartman , Sagi Grimberg Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig , 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> <5951e0f5-cc90-f3de-0083-088fecfd43bb@grimberg.me> <20190725193415.GA12117@kroah.com> From: Logan Gunthorpe Message-ID: <77a3e81d-2542-6782-0fc1-1d25bcc75598@deltatee.com> Date: Thu, 25 Jul 2019 13:41:16 -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: <20190725193415.GA12117@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, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, sagi@grimberg.me, 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 1:34 p.m., Greg Kroah-Hartman wrote: > On Thu, Jul 25, 2019 at 12:02:30PM -0700, Sagi Grimberg 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. >> >> That's definitely not changing. But this is not different than how we >> use the block device or file configuration, this just happen to need the >> nvme controller chardev now to issue I/O. > > So, as was kind of alluded to in another part of the thread, what are > you doing about permissions? It seems that any user/group permissions > are out the window when you have the kernel itself do the opening of the > char device, right? Why is that ok? You can pass it _any_ character > device node and away it goes? What if you give it a "wrong" one? Char > devices are very different from block devices this way. Well the permission question is no different from the block-device case we already have. The user has to be root to configure a target so it has access to the block/char device. Containers and NVMe-of are really not designed to mix and would take a lot of work to make this make any sense (And that's way out of scope of what I'm trying to do here and doesn't change the need for a the cdev_get_by_path()). If the user specifies a non-nvme char device, it is rejected by the code in nvme_ctrl_get_by_path() when it compares the fops. See patch 4. Logan