From: Jan Kara Subject: Re: xfstests generic/130 hang with non-4k block size ext4 on 4.7-rc1 kernel Date: Mon, 20 Jun 2016 13:39:50 +0200 Message-ID: <20160620113950.GD6882@quack2.suse.cz> References: <20160602121750.GC32574@quack2.suse.cz> <20160603101612.GJ10350@eguan.usersys.redhat.com> <20160603115844.GB2470@quack2.suse.cz> <20160608125631.GA19589@quack2.suse.cz> <87oa7a6d1q.fsf@gooddata.com> <20160609150405.GB19882@quack2.suse.cz> <87oa79h9on.fsf@gooddata.com> <20160616132620.GA2106@quack2.suse.cz> <8737odw5xp.fsf@gooddata.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Jan Kara , Holger =?iso-8859-1?Q?Hoffst=E4tte?= , linux-ext4@vger.kernel.org, Jan Kara To: Nikola Pajkovsky Return-path: Received: from mx2.suse.de ([195.135.220.15]:34442 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753612AbcFTLjx (ORCPT ); Mon, 20 Jun 2016 07:39:53 -0400 Content-Disposition: inline In-Reply-To: <8737odw5xp.fsf@gooddata.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu 16-06-16 16:42:58, Nikola Pajkovsky wrote: > Jan Kara writes: >=20 > > On Fri 10-06-16 07:52:56, Nikola Pajkovsky wrote: > >> Jan Kara writes: > >> > On Thu 09-06-16 09:23:29, Nikola Pajkovsky wrote: > >> >> Holger Hoffst=E4tte writes: > >> >>=20 > >> >> > On Wed, 08 Jun 2016 14:56:31 +0200, Jan Kara wrote: > >> >> > (snip) > >> >> >> Attached patch fixes the issue for me. I'll submit it once a= full xfstests > >> >> >> run finishes for it (which may take a while as our server ro= om is currently > >> >> >> moving to a different place). > >> >> >>=20 > >> >> >> Honza > >> >> >> --=20 > >> >> >> Jan Kara > >> >> >> SUSE Labs, CR > >> >> >> From 3a120841a5d9a6c42bf196389467e9e663cf1cf8 Mon Sep 17 00:= 00:00 2001 > >> >> >> From: Jan Kara > >> >> >> Date: Wed, 8 Jun 2016 10:01:45 +0200 > >> >> >> Subject: [PATCH] ext4: Fix deadlock during page writeback > >> >> >>=20 > >> >> >> Commit 06bd3c36a733 (ext4: fix data exposure after a crash) = uncovered a > >> >> >> deadlock in ext4_writepages() which was previously much hard= er to hit. > >> >> >> After this commit xfstest generic/130 reproduces the deadloc= k on small > >> >> >> filesystems. > >> >> > > >> >> > Since you marked this for -stable, just a heads-up that the p= revious patch > >> >> > for the data exposure was rejected from -stable (see [1]) bec= ause it > >> >> > has the mismatching "!IS_NOQUOTA(inode) &&" line, which didn'= t exist > >> >> > until 4.6. I removed it locally but Greg probably wants an of= ficial patch. > >> >> > > >> >> > So both this and the previous patch need to be submitted. > >> >> > > >> >> > [1] http://permalink.gmane.org/gmane.linux.kernel.stable/1807= 4{4,5,6} > >> >>=20 > >> >> I'm just wondering if the Jan's patch is not related to blocked > >> >> processes in following trace. It very hard to hit it and I don'= t have > >> >> any reproducer. > >> > > >> > This looks like a different issue. Does the machine recover itse= lf or is it > >> > a hard hang and you have to press a reset button? > >>=20 > >> The machine is bit bigger than I have pretend. It's 18 vcpu with 1= 60 GB > >> ram and machine has dedicated mount point only for PostgreSQL data= =2E > >>=20 > >> Nevertheless, I was able always to ssh to the machine, so machine = itself > >> was not in hard hang and ext4 mostly gets recover by itself (it to= ok > >> 30min). But I have seen situation, were every process who 'touch' = the ext4 > >> goes immediately to D state and does not recover even after hour. > > > > If such situation happens, can you run 'echo w >/proc/sysrq-trigger= ' to > > dump stuck processes and also run 'iostat -x 1' for a while to see = how much > > IO is happening in the system? That should tell us more. >=20 >=20 > Link to 'echo w >/proc/sysrq-trigger' is here, because it's bit bigge= r > to mail it. >=20 > http://expirebox.com/download/68c26e396feb8c9abb0485f857ccea3a.htm= l Can you upload it again please? I've got to looking at the file only to= day and it is already deleted. Thanks! > I was running iotop and there was traffic roughly ~20 KB/s write. >=20 > What was bit more interesting, was looking at >=20 > cat /proc/vmstat | egrep "nr_dirty|nr_writeback" >=20 > nr_drity had around 240 and was slowly counting up, but nr_writeback = had > ~8800 and was stuck for 120s. Hum, interesting. This would suggest like IO completion got stuck for s= ome reason. We'll see more from the stacktraces hopefully. Honza --=20 Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html