From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753637AbaG2MF7 (ORCPT ); Tue, 29 Jul 2014 08:05:59 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43251 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753148AbaG2MF5 (ORCPT ); Tue, 29 Jul 2014 08:05:57 -0400 Date: Tue, 29 Jul 2014 14:05:55 +0200 From: Jan Kara To: "Theodore Ts'o" Cc: Pavel Machek , linux-kernel@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, jack@suse.cz Subject: Re: Is warn_on() right reply for i/o error? Message-ID: <20140729120555.GB5944@quack.suse.cz> References: <20140724152721.GA4771@amd.pavel.ucw.cz> <20140724192938.GM6673@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140724192938.GM6673@thunk.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 24-07-14 15:29:38, Ted Tso wrote: > On Thu, Jul 24, 2014 at 05:27:22PM +0200, Pavel Machek wrote: > > Hi! > > > > Just... I know, I should not be unscrewing hard drive cover while > > operating. > > > > But on the other hand... WARN_ON() does not sound like right reply for > > a disk failure... right? > > Actually, it can be worse than that. If a hard drive disappears out > from under you while writeback is happening, it's possible to get > crashes in bdi_writeack_workfn() because you can have races between > bdi_unregister() and bdi_writeback_workfn(), since the latter requeues > itself and flush_delayed_work() can return while > bdi_writeback_workfn() is still executing. This should be fixed by 5acda9d12dcf1ad0d9a5a2a7c646de3472fa7555 I wrote in April. But there are certainly other races in that code... > This looks like it's a related problem, where the block device gets > unregistered (and this happens in the block device layer without it > telling the file system that the disk drive is about to disappear out > from under it), and occasionally, Bad Stuff Happens. :-( Yeah. Honza -- Jan Kara SUSE Labs, CR