Date: Tue, 19 Dec 2017 13:48:35 -0600
From: Bruno Wolff III <bruno@wolff.to>
To: Shaohua Li <shli@kernel.org>
Cc: weiping zhang <zwp10758@gmail.com>, 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
Subject: Re: Regression with a0747a859ef6 ("bdi: add error handle for
 bdi_debug_register")
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On Tue, Dec 19, 2017 at 10:24:52 -0800,
  Shaohua Li <shli@kernel.org> wrote:
>
>Not sure if this is MD related, but could you please check if this debug patch
>changes anything?

I'm doing a build now. I do use md to mirror disk partitions between two disks. I do that on another machine that doesn't exhibit the problem, but it is 
i686, not x86_64.