From: James Hogan <james.hogan@imgtec.com>
To: Matt Turner <mattst88@gmail.com>
Cc: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
<linux-nfs@vger.kernel.org>,
Manuel Lauss <manuel.lauss@gmail.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: NFS corruption, fixed by echo 1 > /proc/sys/vm/drop_caches -- next debugging steps?
Date: Mon, 13 Mar 2017 09:47:57 +0000 [thread overview]
Message-ID: <20170313094757.GI2878@jhogan-linux.le.imgtec.org> (raw)
In-Reply-To: <CAEdQ38HcOgAT6wJWWKY3P0hzYwkBGSQkRSQ2a=eaGmD6c6rwXA@mail.gmail.com>
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On Sun, Mar 12, 2017 at 06:43:47PM -0700, Matt Turner wrote:
> On a Broadcom BCM91250a MIPS system I can reliably trigger NFS
> corruption on the first file read.
>
> To demonstrate, I downloaded five identical copies of the gcc-5.4.0
> source tarball. On the NFS server, they hash to the same value:
>
> server distfiles # md5sum gcc-5.4.0.tar.bz2*
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.1
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.3
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.4
>
> On the MIPS system (the NFS client):
>
> bcm91250a-le distfiles # md5sum gcc-5.4.0.tar.bz2.2
> 35346975989954df8a8db2b034da610d gcc-5.4.0.tar.bz2.2
> bcm91250a-le distfiles # md5sum gcc-5.4.0.tar.bz2*
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.1
> 35346975989954df8a8db2b034da610d gcc-5.4.0.tar.bz2.2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.3
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.4
>
> The first file read will contain some corruption, and it is persistent until...
>
> bcm91250a-le distfiles # echo 1 > /proc/sys/vm/drop_caches
> bcm91250a-le distfiles # md5sum gcc-5.4.0.tar.bz2*
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.1
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.2
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.3
> 4c626ac2a83ef30dfb9260e6f59c2b30 gcc-5.4.0.tar.bz2.4
>
> the caches are dropped, at which point it reads back properly.
>
> Note that the corruption is different across reboots, both in the size
> of the corruption and the location. I saw 1900~ and 1400~ byte
> sequences corrupted on separate occasions, which don't correspond to
> the system's 16kB page size.
>
> I've tested kernels from v3.19 to 4.11-rc1+ (master branch from
> today). All exhibit this behavior with differing frequencies. Earlier
> kernels seem to reproduce the issue less often, while more recent
> kernels reliably exhibit the problem every boot.
>
> How can I further debug this?
It smells a bit like a DMA / caching issue.
Can you provide a full kernel log. That might provide some information
about caching that might be relevant (e.g. does dcache have aliases?).
Cheers
James
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next prev parent reply other threads:[~2017-03-13 9:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-13 1:43 NFS corruption, fixed by echo 1 > /proc/sys/vm/drop_caches -- next debugging steps? Matt Turner
2017-03-13 9:47 ` James Hogan [this message]
2017-03-13 17:17 ` Matt Turner
2017-03-15 9:25 ` Ralf Baechle
2017-12-08 7:00 ` Matt Turner
2017-12-08 7:54 ` Matt Turner
2017-12-08 13:42 ` Eric Dumazet
2017-12-08 13:52 ` Eric Dumazet
2017-12-08 20:26 ` Matt Turner
2017-12-08 21:16 ` Eric Dumazet
2017-12-09 21:03 ` Matt Turner
2017-12-09 21:37 ` Eric Dumazet
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