linux-kernel - Re: Regression with a0747a859ef6 ("bdi: add error handle for bdi_debug

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Message-ID: <20171221181531.GA21050@wolff.to>
Date:   Thu, 21 Dec 2017 12:15:31 -0600
From:   Bruno Wolff III <bruno@...ff.to>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     weiping zhang <zwp10758@...il.com>,
        Laura Abbott <labbott@...hat.com>, Jan Kara <jack@...e.cz>,
        linux-mm@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        regressions@...mhuis.info,
        weiping zhang <zhangweiping@...ichuxing.com>,
        linux-block@...r.kernel.org
Subject: Re: Regression with a0747a859ef6 ("bdi: add error handle for
 bdi_debug_register")

On Thu, Dec 21, 2017 at 10:02:15 -0700,
  Jens Axboe <axboe@...nel.dk> wrote:
>On 12/21/17 9:42 AM, Bruno Wolff III wrote:
>> On Thu, Dec 21, 2017 at 23:48:19 +0800,
>>   weiping zhang <zwp10758@...il.com> wrote:
>>>> output you want. I never saw it for any kernels I compiled myself. Only when
>>>> I test kernels built by Fedora do I see it.
>>> see it every boot ?
>>
>> I don't look every boot. The warning gets scrolled of the screen. Once I see
>> the CPU hang warnings I know the boot is failing. I don't always look
>> at journalctl later to see what's there.
>
>I'm going to revert a0747a859ef6 for now, since we're now 8 days into this
>and no progress has been made on fixing it.

One important thing I have just found is that it looks like the problem 
only happens when booting in enforcing mode. If I boot in permissive 
mode it does not happen. My home machines are currently set to boot in 
permissive mode and I'll test this evening to see if I can reproduce the 
problem if I change them to enforcing mode. If so I'll be able to do lots 
of testing during my vacation.