From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751603Ab3HSXCp (ORCPT ); Mon, 19 Aug 2013 19:02:45 -0400 Received: from mail-qa0-f43.google.com ([209.85.216.43]:64882 "EHLO mail-qa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751299Ab3HSXCo (ORCPT ); Mon, 19 Aug 2013 19:02:44 -0400 Date: Mon, 19 Aug 2013 19:02:40 -0400 From: Tejun Heo To: Peter Wu Cc: Alan Stern , Kernel development list , Jens Axboe Subject: Re: [PATCH] writeback: fix NULL dereference when device is gone Message-ID: <20130819230240.GA6869@mtj.dyndns.org> References: <5177367.3UXkd1Z6lS@al> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5177367.3UXkd1Z6lS@al> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 20, 2013 at 12:45:53AM +0200, Peter Wu wrote: > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 68851ff..6e38a8b 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1007,7 +1007,8 @@ void bdi_writeback_workfn(struct work_struct *work) > struct backing_dev_info *bdi = wb->bdi; > long pages_written; > > - set_worker_desc("flush-%s", dev_name(bdi->dev)); > + if (bdi->dev) > + set_worker_desc("flush-%s", dev_name(bdi->dev)); Hmmm... bdi->dev is cleared after bdi_wb_shutdown() so the work item should no longer be running. It seems like something is queueing the work item after shutdown and the proper fix would be finding out which and fixing it. Can you please verify whether adding WARN_ON(!bdi->dev) in bdi_wakeup_thread_delayed() trigger anything? Thanks. -- tejun