From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753223AbaB0Vd3 (ORCPT ); Thu, 27 Feb 2014 16:33:29 -0500 Received: from cantor2.suse.de ([195.135.220.15]:47144 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751986AbaB0Vcz (ORCPT ); Thu, 27 Feb 2014 16:32:55 -0500 Date: Thu, 27 Feb 2014 22:32:52 +0100 From: Jan Kara To: Tejun Heo Cc: Jan Kara , linux-fsdevel@vger.kernel.org, LKML , Jens Axboe , stable@vger.kernel.org Subject: Re: [PATCH 2/2] bdi: Avoid oops on device removal Message-ID: <20140227213252.GA18830@quack.suse.cz> References: <1393367354-5172-1-git-send-email-jack@suse.cz> <1393367354-5172-3-git-send-email-jack@suse.cz> <20140227200748.GA466@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140227200748.GA466@htj.dyndns.org> 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 Thu 27-02-14 15:07:48, Tejun Heo wrote: > Hello, > > On Tue, Feb 25, 2014 at 11:29:14PM +0100, Jan Kara wrote: > > +static void bdi_wakeup_thread(struct backing_dev_info *bdi) > > +{ > > + spin_lock_bh(&bdi->wb_lock); > > + if (test_bit(BDI_registered, &bdi->state)) > > + mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0); > > + spin_unlock_bh(&bdi->wb_lock); > > +} > > I wonder whether this can be smarter without requiring wb_lock each > timer but this probably is the simplest for -stable backports. We could be clever, check whether the work is already queued for execution and bail out without taking wb_lock if yes (that would also save us some unnecessary juggling in try_to_grab_pending() for the situation were the work is already queued). But I'm not sure how to cleanly implement this... > > static void bdi_queue_work(struct backing_dev_info *bdi, > > struct wb_writeback_work *work) > > { > > trace_writeback_queue(bdi, work); > > > > spin_lock_bh(&bdi->wb_lock); > > + if (!test_bit(BDI_registered, &bdi->state)) { > > + if (work->done) > > + complete(work->done); > > + goto out_unlock; > > + } > > list_add_tail(&work->list, &bdi->work_list); > > - spin_unlock_bh(&bdi->wb_lock); > > - > > mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0); > > +out_unlock: > > + spin_unlock_bh(&bdi->wb_lock); > > } > > > > + > > + > > Why three blank lines? A mistake. Will fix. > Other than that, > > Reviewed-by: Tejun Heo Thanks! Honza -- Jan Kara SUSE Labs, CR