linux-ext4 - Re: Frequent ext4 oopses with 4.4.0 on Intel NUC6i3SYB

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Message-ID: <90dfe18f-9fe7-819d-c410-cdd160644ab7@gmx.de>
Date:   Tue, 4 Oct 2016 18:50:55 +0200
From:   Johannes Bauer <dfnsonfsduifb@....de>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Frequent ext4 oopses with 4.4.0 on Intel NUC6i3SYB

On 04.10.2016 10:41, Jan Kara wrote:

> The problem looks like memory corruption:
[...]

Huh, very interesting -- thanks for the walkthrough!

> Anyway, adding linux-mm to CC since this does not look ext4 related but
> rather mm related issue.
> 
> Bugs like these are always hard to catch, usually it's some flaky device
> driver, sometimes also flaky HW. You can try running kernel with various
> debug options enabled in a hope to catch the code corrupting memory
> earlier - e.g. CONFIG_DEBUG_PAGE_ALLOC sometimes catches something,
> CONFIG_SLAB_DEBUG can be useful as well. Another option is to get a
> crashdump when the oops happens (although that's going to be a pain to
> setup on such a small machine) and then look at which places point to
> the corrupted memory - sometimes you can find old structures pointing to
> the place and find the use-after-free issue or stuff like that...

Uhh, that sounds painful. So I'm following Ted's advice and building
myself a 4.8 as we speak.

If the problem is fixed, would it be of any help to trace the source by
going back to the 4.4.0 and reproduce with the debug symbols you
mentioned? I don't think a memdump would be difficult on the machine
(while it certainly has a small form factor, it's got a 1 TB hdd and 16
GB of RAM, so it's not really that small).

Cheers,
Johannes

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