From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758586AbdJMPfS (ORCPT ); Fri, 13 Oct 2017 11:35:18 -0400 Received: from mx1.mpynet.fi ([82.197.21.84]:45563 "EHLO mx1.mpynet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758512AbdJMPfP (ORCPT ); Fri, 13 Oct 2017 11:35:15 -0400 Date: Fri, 13 Oct 2017 18:35:13 +0300 From: Rakesh Pandit To: Christoph Hellwig CC: Matias =?iso-8859-1?Q?Bj=F8rling?= , , , Subject: Re: [GIT PULL 02/58] lightnvm: prevent bd removal if busy Message-ID: <20171013153513.GA3755@hercules.tuxera.com> References: <20171013124647.32668-1-m@bjorling.me> <20171013124647.32668-3-m@bjorling.me> <20171013145809.GA16745@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20171013145809.GA16745@infradead.org> User-Agent: Mutt/1.8.0 (2017-02-23) X-ClientProxiedBy: tuxera-exch.ad.tuxera.com (10.20.48.11) To tuxera-exch.ad.tuxera.com (10.20.48.11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 13, 2017 at 07:58:09AM -0700, Christoph Hellwig wrote: > On Fri, Oct 13, 2017 at 02:45:51PM +0200, Matias Bjørling wrote: > > From: Rakesh Pandit > > > > When a virtual block device is formatted and mounted after creating > > with "nvme lnvm create... -t pblk", a removal from "nvm lnvm remove" > > would result in this: > > > > 446416.309757] bdi-block not registered > > [446416.309773] ------------[ cut here ]------------ > > [446416.309780] WARNING: CPU: 3 PID: 4319 at fs/fs-writeback.c:2159 > > __mark_inode_dirty+0x268/0x340 > > > > Ideally removal should return -EBUSY as block device is mounted after > > formatting. This patch tries to address this checking if whole device > > or any partition of it already mounted or not before removal. > > How is this different from any other block device that can be > removed even if a file system is mounted? One can create many virtual block devices on top of physical using: nvme lnvm create ... -t pblk And remove them using: nvme lnvm remove Because the block devices are virtual in nature created by a program I was expecting removal to tell me they are busy instead of bdi-block not registered following by a WARNING (above). My use case was writing automatic test case but I assumed this is useful in general. > > > > > Whole device is checked using "bd_super" member of block device. This > > member is always set once block device has been mounted using a > > filesystem. Another member "bd_part_count" takes care of checking any > > if any partitions are under use. "bd_part_count" is only updated > > under locks when partitions are opened or closed (first open and last > > release). This at least does take care sending -EBUSY if removal is > > being attempted while whole block device or any partition is mounted. > > > > That's a massive layering violation, and a driver has no business > looking at these fields. Okay, I didn't consider this earlier. I would suggest a revert for this.