From: Jan Kara Subject: Re: [BUG] aborted ext4 leads to inifinity loop in balance_dirty_pages Date: Wed, 9 Nov 2011 12:15:24 +0100 Message-ID: <20111109111524.GA1025@quack.suse.cz> References: <4EA6A5E5.2050604@sx.jp.nec.com> <20111025134045.GB8072@quack.suse.cz> <4EAA3EE7.4040802@sx.jp.nec.com> <20111108000335.GA7518@quack.suse.cz> <4EBA39A4.3040708@sx.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , ext4 , Theodore Tso , Andreas Dilger To: Kazuya Mio Return-path: Received: from cantor2.suse.de ([195.135.220.15]:38321 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753655Ab1KILP1 (ORCPT ); Wed, 9 Nov 2011 06:15:27 -0500 Content-Disposition: inline In-Reply-To: <4EBA39A4.3040708@sx.jp.nec.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed 09-11-11 17:28:20, Kazuya Mio wrote: > 2011/11/08 9:03, Jan Kara wrote: > > On Fri 28-10-11 14:34:31, Kazuya Mio wrote: > >> 2011/10/25 22:40, Jan Kara wrote: > >>> Please no. Generally this boils down to what do we do with dirty data > >>> when there's error in writing them out. Currently we just throw them away > >>> (e.g. in media error case) but I don't think that's a generally good thing > >>> because e.g. admin may want to copy the data to other working storage or > >>> so. So I think we should rather keep the data and provide a mechanism for > >>> userspace to ask kernel to get rid of the data (so that we don't eventually > >>> run OOM). > >> > >> I see. I agree with you. > >> > >>>> Do you have any ideas? > >>> So the question is what would you like to achieve. If you just want to > >>> unblock a thread then a solution would be to make a thread at > >>> balance_dirty_pages() killable. If generally you want to get rid of dirty > >>> memory, then I don't have a really good answer but throwing dirty data away > >>> seems like a bad answer to me. > >> > >> The problem is that we cannot unmount the corrupted filesystem due to > >> un-killable dd process. We must bring down the system to resume the service > >> with no dirty pages. I think it is important for the service continuity > >> to be able to kill the thread handling in balance_dirty_pages(). > > OK, attached are two patches based on latest Linus's tree that should > > make your task killable. Can you test them? > > I'm trying to reproduce now, but it's hard. Could you wait a few days? Sure, take as much time as you need. Honza -- Jan Kara SUSE Labs, CR