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From: weiping zhang <zwp10758@gmail.com>
Date: Fri, 15 Dec 2017 10:04:32 +0800
Message-ID: <CAA70yB6spi5c38kFVidRsJVaYc3W9tvpZz6wy+28rK7oeefQfw@mail.gmail.com>
Subject: Re: Regression with a0747a859ef6 ("bdi: add error handle for bdi_debug_register")
To: Bruno Wolff III <bruno@wolff.to>
Cc: Laura Abbott <labbott@redhat.com>, Jan Kara <jack@suse.cz>,
        Jens Axboe <axboe@kernel.dk>, linux-mm@kvack.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        regressions@leemhuis.info, linux-block@vger.kernel.org
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2017-12-15 9:44 GMT+08:00 Bruno Wolff III <bruno@wolff.to>:
> On Fri, Dec 15, 2017 at 09:22:21 +0800,
>  weiping zhang <zwp10758@gmail.com> wrote:
>>
>>
>> Thanks your testing, but I cann't find WARN_ON in device_add_disk from
>> this boot1.log, could you help reproduce that issue? And does this issue
>> can be
>> triggered at every bootup ?
>
>
> I don't know what you need for the first question. When I am physically at
> the machine I can do test reboots. If you have something specific you want
> me to try I should be able to.
>
> Every time I boot with the problem commit, the boot never completes. However
> it does seem to get pretty far. I get multiple register dumps every time.
> After a while (a few minutes) I reboot to a wrking kernel.
>
> The output I included is from: journalctl -k -b -1
> If you think it would be better to see more than dmesg output let me know.
I just want to know WARN_ON WHAT in device_add_disk,
if bdi_register_owner return error code, it may fail at any step of following:

bdi_debug_root is NULL
bdi->debug_dir is NULL
bdi->debug_stats is NULL

so I want see the WARN_ON as you paste before, also my DEBUG log will help
to find which step fail.