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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 6EB45C76190 for ; Thu, 25 Jul 2019 19:34:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BAD9218F0 for ; Thu, 25 Jul 2019 19:34:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564083259; bh=XmYuwxHf0VVKO+yWC7+GNQPhvgKyB5pGg9W5noBtV5A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=RUpOl9wp+/1V4n1lM5voyWrsgHhp+86AsvM5vmNyXawZVuV2kmR6WYOZGDFae96Z+ 5iO2w8eQCTBoBOX3DEE9xYZCzkdaiknKSI4abQyT77CaMMrhAq3XA3XccyGHHDD0OX IMiGZnsS3pWR3rV/ZbJgTneRmK7QlbZ3ow3nRHZQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726230AbfGYTeS (ORCPT ); Thu, 25 Jul 2019 15:34:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:43026 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726126AbfGYTeS (ORCPT ); Thu, 25 Jul 2019 15:34:18 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F1FDC218EA; Thu, 25 Jul 2019 19:34:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564083257; bh=XmYuwxHf0VVKO+yWC7+GNQPhvgKyB5pGg9W5noBtV5A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=d3PTiS9N52mYF5DGcUuY4yOnuzZS4zliBNIktBb8T/57DhVRGzhaH7j5HmmWgnryx C9l2UR21v5CIglf+hjNiv28E1LxVTEO0pmbHVRsvvVILqePuJLvSGSQ2VGdYSU4UX3 7o7ICHpuPnOeHJyd0e42GVoe16EdvBsM6kt32IU8= Date: Thu, 25 Jul 2019 21:34:15 +0200 From: Greg Kroah-Hartman To: Sagi Grimberg Cc: Logan Gunthorpe , 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 Subject: Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path() Message-ID: <20190725193415.GA12117@kroah.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5951e0f5-cc90-f3de-0083-088fecfd43bb@grimberg.me> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. thanks, greg k-h