From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail-eopbgr760078.outbound.protection.outlook.com ([40.107.76.78]:45519
        "EHLO NAM02-CY1-obe.outbound.protection.outlook.com"
        rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
        id S1728883AbeKJVBo (ORCPT <rfc822;linux-fsdevel@vger.kernel.org>);
        Sat, 10 Nov 2018 16:01:44 -0500
From: Jan Glauber <Jan.Glauber@cavium.com>
To: Will Deacon <will.deacon@arm.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: dcache_readdir NULL inode oops
Date: Sat, 10 Nov 2018 11:17:03 +0000
Message-ID: <20181110111656.GA16667@hc>
References: <20181109143744.GA12128@hc> <20181109155856.GC2091@brain-police>
In-Reply-To: <20181109155856.GC2091@brain-police>
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-ID: <3DBA5766A495184FBAA4713EA7AB162D@namprd07.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Fri, Nov 09, 2018 at 03:58:56PM +0000, Will Deacon wrote:
> On Fri, Nov 09, 2018 at 02:37:51PM +0000, Jan Glauber wrote:
> > I'm seeing the following oops reproducible with upstream kernel on arm6=
4
> > (ThunderX2):
>=20
> [...]
>=20
> > It happens after 1-3 hours of running 'stress-ng --dev 128'. This testc=
ase
> > does a scandir of /dev and then calls random stuff like ioctl, lseek,
> > open/close etc. on the entries. I assume no files are deleted under /de=
v
> > during the testcase.
> >
> > The NULL pointer is the inode pointer of next. The next dentry->d_flags=
 is
> > DCACHE_RCUACCESS when this happens.
> >
> > Any hints on how to further debug this?
>=20
> Can you reproduce the issue with vanilla -rc1 and do you have a "known go=
od"
> kernel?

I can try out -rc1, but IIRC this wasn't bisectible as the bug was present =
at
least back to 4.14. I need to double check that as there were other issues
that are resolved now so I may confuse things here. I've defintely seen
the same bug with 4.18.

Unfortunately I lost access to the machine as our data center seems to be
moving currently so it might take some days until I can try -rc1.

thanks,
Jan