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 3C01DC7618B for ; Fri, 26 Jul 2019 15:46:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 15D732166E for ; Fri, 26 Jul 2019 15:46:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727643AbfGZPqz (ORCPT ); Fri, 26 Jul 2019 11:46:55 -0400 Received: from ale.deltatee.com ([207.54.116.67]:34250 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727389AbfGZPqz (ORCPT ); Fri, 26 Jul 2019 11:46:55 -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 1hr2Qh-0002Yy-EH; Fri, 26 Jul 2019 09:46:48 -0600 To: Sagi Grimberg , Al Viro Cc: Matthew Wilcox , Greg Kroah-Hartman , Jens Axboe , Chaitanya Kulkarni , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, Stephen Bates , linux-block@vger.kernel.org, Keith Busch , linux-fsdevel@vger.kernel.org, Max Gurtovoy , Christoph Hellwig References: <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> <20190725190024.GD30641@bombadil.infradead.org> <27943e06-a503-162e-356b-abb9e106ab2e@grimberg.me> <20190725191124.GE30641@bombadil.infradead.org> <425dd2ac-333d-a8c4-ce49-870c8dadf436@deltatee.com> <20190725235502.GJ1131@ZenIV.linux.org.uk> <7f48a40c-6e0f-2545-a939-45fc10862dfd@grimberg.me> From: Logan Gunthorpe Message-ID: Date: Fri, 26 Jul 2019 09:46:40 -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: <7f48a40c-6e0f-2545-a939-45fc10862dfd@grimberg.me> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 68.147.80.180 X-SA-Exim-Rcpt-To: hch@lst.de, maxg@mellanox.com, linux-fsdevel@vger.kernel.org, kbusch@kernel.org, linux-block@vger.kernel.org, sbates@raithlin.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Chaitanya.Kulkarni@wdc.com, axboe@fb.com, gregkh@linuxfoundation.org, willy@infradead.org, viro@zeniv.linux.org.uk, sagi@grimberg.me 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 10:29 p.m., Sagi Grimberg wrote: > >>>>>>>> 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 suppose we could echo a string of the file descriptor number there, >>>>>> and look up the fd in the process' file descriptor table ... >>>>> >>>>> Assuming that there is a open handle somewhere out there... >>> >>> Yes, that would be a step backwards from an interface. The user would >>> then need a special process to open the fd and pass it through configfs. >>> They couldn't just do it with basic bash commands. >> >> First of all, they can, but... WTF not have filp_open() done right there? >> Yes, by name.  With permission checks done.  And pick your object from >> the >> sodding struct file you'll get. >> >> What's the problem?  Why do you need cdev lookups, etc., when you are >> dealing with files under your full control?  Just open them and use >> ->private_data or whatever you set in ->open() to access the damn thing. >> All there is to it... > Oh this is so much simpler. There is really no point in using anything > else. Just need to remember to compare f->f_op to what we expect to make > sure that it is indeed the same device class. Yes, that sounds like a good idea. I'll do this for v2. Thanks, Logan