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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
Thread-Topic: dcache_readdir NULL inode oops
Thread-Index: AQHUeDnKfcShvdBH+0+6hZ8Ik/l9/A==
Date:   Sat, 10 Nov 2018 11:17:03 +0000
Message-ID: <20181110111656.GA16667@hc>
References: <20181109143744.GA12128@hc> <20181109155856.GC2091@brain-police>
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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