From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id BC7AB6B0038 for ; Thu, 21 Dec 2017 20:29:33 -0500 (EST) Received: by mail-wr0-f200.google.com with SMTP id l33so15827544wrl.5 for ; Thu, 21 Dec 2017 17:29:33 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id l13sor11554401edj.1.2017.12.21.17.29.32 for (Google Transport Security); Thu, 21 Dec 2017 17:29:32 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1513902570.3132.22.camel@HansenPartnership.com> References: <20171221130057.GA26743@wolff.to> <20171221151843.GA453@wolff.to> <20171221153631.GA2300@wolff.to> <20171221164221.GA23680@wolff.to> <14f04d43-728a-953f-e07c-e7f9d5e3392d@kernel.dk> <1513902570.3132.22.camel@HansenPartnership.com> From: weiping zhang Date: Fri, 22 Dec 2017 09:29:31 +0800 Message-ID: Subject: Re: Regression with a0747a859ef6 ("bdi: add error handle for bdi_debug_register") Content-Type: multipart/alternative; boundary="94eb2c1affd09f6b320560e3bf92" Sender: owner-linux-mm@kvack.org List-ID: To: James Bottomley Cc: Jens Axboe , Bruno Wolff III , Laura Abbott , Jan Kara , "linux-mm@kvack.org" , Linux Kernel Mailing List , "regressions@leemhuis.info" , weiping zhang , "linux-block@vger.kernel.org" --94eb2c1affd09f6b320560e3bf92 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 2017=E5=B9=B412=E6=9C=8822=E6=97=A5=E6=98=9F=E6=9C=9F=E4=BA=94=EF=BC=8CJame= s Bottomley =E5=86=99=E9=81=93=EF= =BC=9A > On Thu, 2017-12-21 at 10:02 -0700, Jens Axboe wrote: > > On 12/21/17 9:42 AM, Bruno Wolff III wrote: > > > > > > On Thu, Dec 21, 2017 at 23:48:19 +0800, > > > weiping zhang 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. > > There is a dummy function in this file, if DEBUG_FS =3DN=EF=BC=8C > I think this is correct. If you build the kernel with > CONFIG_DEBUG_FS=3DN, you're definitely going to get the same hang > (because the debugfs_ functions fail with -ENODEV and the bdi will > never get registered). This alone leads me to suspect the commit is > bogus because it's a randconfig/test accident waiting to happen. > We should still root cause the debugfs failure in this case, but I > really think debugfs files should be treated as optional, so a failure > in setting them up should translate to some sort of warning not a > failure to set up the bdi. > > Yes, its just for debug, has no effect on gendisk(include weiteback), > James > > --94eb2c1affd09f6b320560e3bf92 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

2017=E5=B9=B412=E6=9C=8822=E6=97=A5=E6=98=9F=E6=9C=9F=E4=BA=94=EF= =BC=8CJames Bottomley <James.Bottomley@hansenpartnership.com> =E5=86=99=E9=81=93=EF= =BC=9A
On Thu, 2017-12-21 at 10:02 -0700,= Jens Axboe wrote:
> On 12/21/17 9:42 AM, Bruno Wolff III wrote:
> >
> > On Thu, Dec 21, 2017 at 23:48:19 +0800,
> > =C2=A0 weiping zhang <zw= p10758@gmail.com> wrote:
> > >
> > > >
> > > > output you want. I never saw it for any kernels I compi= led
> > > > myself. Only when I test kernels built by Fedora do I s= ee it.
> > > > see it every boot ?
> >
> > I don't look every boot. The warning gets scrolled of the scr= een.
> > 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 da= ys into
> this and no progress has been made on fixing it.

There is a dummy function in this file, if DEBUG_FS = =3DN=EF=BC=8C=C2=A0
I think this is correct.=C2=A0 If you build the kernel with
CONFIG_DEBUG_FS=3DN, you're definitely going to get the same hang
(because the debugfs_ functions fail with -ENODEV and the bdi will
never get registered).=C2=A0 This alone leads me to suspect the commit is bogus because it's a randconfig/test accident waiting to happen.
We should still root cause the debugfs failure in this case, but I
really think debugfs files should be treated as optional, so a failure
in setting them up should translate to some sort of warning not a
failure to set up the bdi.

Yes, its just for debug, has no effect on gendisk(inc= lude weiteback),=C2=A0
James

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