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 57475C76190 for ; Thu, 25 Jul 2019 20:37:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 380482166E for ; Thu, 25 Jul 2019 20:37:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726897AbfGYUhV (ORCPT ); Thu, 25 Jul 2019 16:37:21 -0400 Received: from ale.deltatee.com ([207.54.116.67]:43852 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726741AbfGYUhU (ORCPT ); Thu, 25 Jul 2019 16:37:20 -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 1hqkU7-0005Lc-87; Thu, 25 Jul 2019 14:37:08 -0600 To: Keith Busch Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig , Sagi Grimberg , Jens Axboe , Chaitanya Kulkarni , Max Gurtovoy , Stephen Bates References: <20190725172335.6825-1-logang@deltatee.com> <20190725172335.6825-5-logang@deltatee.com> <20190725175023.GA30641@bombadil.infradead.org> <20190725195835.GA7317@localhost.localdomain> <5dd6a41d-21c4-cf8d-a81d-271549de6763@deltatee.com> <20190725203118.GB7317@localhost.localdomain> From: Logan Gunthorpe Message-ID: <3bb266ae-abf3-0146-5d93-e7a600453493@deltatee.com> Date: Thu, 25 Jul 2019 14:37:05 -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: <20190725203118.GB7317@localhost.localdomain> 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: sbates@raithlin.com, maxg@mellanox.com, Chaitanya.Kulkarni@wdc.com, axboe@fb.com, 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, willy@infradead.org, kbusch@kernel.org X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v6 04/16] nvme-core: introduce nvme_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-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2019-07-25 2:31 p.m., Keith Busch wrote: > On Thu, Jul 25, 2019 at 02:28:28PM -0600, Logan Gunthorpe wrote: >> >> >> On 2019-07-25 1:58 p.m., Keith Busch wrote: >>> On Thu, Jul 25, 2019 at 11:54:18AM -0600, Logan Gunthorpe wrote: >>>> >>>> >>>> On 2019-07-25 11:50 a.m., Matthew Wilcox wrote: >>>>> On Thu, Jul 25, 2019 at 11:23:23AM -0600, Logan Gunthorpe wrote: >>>>>> nvme_get_by_path() is analagous to blkdev_get_by_path() except it >>>>>> gets a struct nvme_ctrl from the path to its char dev (/dev/nvme0). >>>>>> >>>>>> The purpose of this function is to support NVMe-OF target passthru. >>>>> >>>>> I can't find anywhere that you use this in this patchset. >>>>> >>>> >>>> Oh sorry, the commit message is out of date the function was actually >>>> called nvme_ctrl_get_by_path() and it's used in Patch 10. >>> >>> Instead of by path, could we have configfs take something else, like >>> the unique controller instance or serial number? I know that's different >>> than how we handle blocks and files, but that way nvme core can lookup >>> the cooresponding controller without adding new cdev dependencies. >> >> Well the previous version of the patchset just used the ctrl name >> ("nvme1") and looped through all the controllers to find a match. But >> this sucks because of the inconsistency and the fact that the name can >> change if hardware changes and the number changes. Allowing the user to >> make use of standard udev rules seems important to me. > > Should we then create a new udev rule for persistent controller > names? /dev/nvme1 may not be the same controller each time you refer > to it. Udev can only create symlinks from /dev/nvme0 to /dev/nvme-persistent-name and users can do this as they need now. No changes needed. My point was if we use the ctrl name (nvme0) as a reference then the kernel can't make use of these symlinks or anything udev does seeing that name is internal to the kernel only. If we use cdev_get_by_path()/nvme_ctrl_get_by_path() then this isn't a problem as we can open a symlink to /dev/nvme0 without any issues. Logan