From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757793Ab2AERMD (ORCPT ); Thu, 5 Jan 2012 12:12:03 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:36480 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755188Ab2AERMA (ORCPT ); Thu, 5 Jan 2012 12:12:00 -0500 Date: Thu, 5 Jan 2012 09:11:57 -0800 From: Tejun Heo To: Alan Stern Cc: "Eric W. Biederman" , "Theodore Ts'o" , Kernel development list , Greg Kroah-Hartman , Kay Sievers Subject: Re: Revoking filesystems [was Re: Sysfs attributes racing with unregistration] Message-ID: <20120105171157.GA18486@google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Jan 05, 2012 at 11:47:54AM -0500, Alan Stern wrote: > One problem (which was reported by a user last spring) is that > del_gendisk() calls device_del() for the disk and bdi_unregister() for > the disk's backing_dev_info structure. Now, del_gendisk will leave the > data structure in memory until the disk's refcount drops to 0, but > bdi_unregister ignores refcounts and simply erases the bdi->dev > pointer. Once this happens, any attempt to call mark_buffer_dirty() > (for example, by ext4_commit_super) will cause an oops. Yeah, there were multiple bugs in block device hot-removal path. I got some of them fixed recently but didn't get to the bdi one yet. It's a bug and needs to be fixed regardless of fs revoke support. Thanks. -- tejun