From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:47536 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbdAWOmo (ORCPT ); Mon, 23 Jan 2017 09:42:44 -0500 Date: Mon, 23 Jan 2017 09:42:08 -0500 From: Josef Bacik Subject: Re: [PATCH 4/4] nbd: add a nbd-control interface To: Greg KH CC: , , , , Message-ID: <1485182528.9861.22@smtp.office365.com> In-Reply-To: <20170121090531.GB27048@kroah.com> References: <1484949412-6903-1-git-send-email-jbacik@fb.com> <1484949412-6903-4-git-send-email-jbacik@fb.com> <20170121090531.GB27048@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Sat, Jan 21, 2017 at 4:05 AM, Greg KH wrote: > On Fri, Jan 20, 2017 at 04:56:52PM -0500, Josef Bacik wrote: >> This patch mirrors the loop back device behavior with a few >> changes. First >> there is no DEL operation as NBD doesn't get as much churn as loop >> devices do. >> Secondly the GET_NEXT operation can optionally create a new NBD >> device or not. >> Our infrastructure people want to not allow NBD to create new >> devices as it >> causes problems for them in containers. However allow this to be >> optional as >> things like the OSS NBD client probably doesn't care and would like >> to just be >> given a device to use. >> >> Signed-off-by: Josef Bacik > > A random char device with odd ioctls? Why? There's no other > configuration choice you could possibly use? Where is the userspace > tool that uses this new kernel api? > > You aren't passing in structures to the ioctl, so why does this HAVE > to > be an ioctl? Again, this is how loop does it so I assumed a known, regularly used API was the best bet. I can do literally anything, but these interfaces have to be used by other people, including internal people. The /dev/whatever-control is a well established way for interacting with dynamic device drivers (loop, DM, btrfs), so that's what I went with. Thanks, Josef