From: Wu Fengguang <wfg@linux.intel.com>
To: "Илья Тумайкин" <librarian_rus@yahoo.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: A regression in recent 3.2 kernel: bdi_dirty_limit() divide error
Date: Tue, 10 Jan 2012 22:38:05 +0800 [thread overview]
Message-ID: <20120110143805.GA8320@localhost> (raw)
In-Reply-To: <1326205945.62365.YahooMailClassic@web161603.mail.bf1.yahoo.com>
On Tue, Jan 10, 2012 at 06:32:25AM -0800, Илья Тумайкин wrote:
> Hello, Mr. Fengguang.
>
> This latter patch fixed the problem completely! I've tested vanilla 3.2 with both patches applied and with only the latter one, results are the same:
> - first of all the initial problem solved. I have no "divide error" (not sure if this panic) now.
> - doing daily desktop stuff (e.g. web browsing, movie playback, book reading etc) also without any errors as well as compiling packages.
>
> So, I can confirm the problem is solved completely.
> Thank you and your colleagues very much for you fast response and active help! I am very grateful!
Ilya, thank you too for your report and testing! I'll submit the patch right now.
Thanks,
Fengguang
> --- Пн, 9.1.12, Wu Fengguang <wfg@linux.intel.com> пишет:
>
> > От: Wu Fengguang <wfg@linux.intel.com>
> > Тема: Re: A regression in recent 3.2 kernel: bdi_dirty_limit() divide error
> > Кому: "Peter Zijlstra" <a.p.zijlstra@chello.nl>
> > Копия: "Илья Тумайкин" <librarian_rus@yahoo.com>, "LKML" <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org
> > Дата: Понедельник, 9 январь 2012, 7:04
> > On Sun, Jan 08, 2012 at 11:19:14AM
> > +0100, Peter Zijlstra wrote:
> >
> > > But even then, we limit PROP_MAX_SHIFT to
> > 3*BITS_PER_LONG/4, I don't
> > > think that could ever overflow.
> >
> > do_div() only uses the lower 32 bit value of the 64 bit
> > denominator,
> > which may happen to be 0.
> >
> > The denominator is not really 64 bit, but limited by
> > PROP_MAX_SHIFT =
> > 48 bit, however that upper limit looks not enough.
> >
> > Ilya, would you help try the attached patch instead?
> >
> > Thanks,
> > Fengguang
> >
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WARNING: multiple messages have this Message-ID (diff)
From: Wu Fengguang <wfg@linux.intel.com>
To: "Илья Тумайкин" <librarian_rus@yahoo.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: A regression in recent 3.2 kernel: bdi_dirty_limit() divide error
Date: Tue, 10 Jan 2012 22:38:05 +0800 [thread overview]
Message-ID: <20120110143805.GA8320@localhost> (raw)
In-Reply-To: <1326205945.62365.YahooMailClassic@web161603.mail.bf1.yahoo.com>
On Tue, Jan 10, 2012 at 06:32:25AM -0800, Илья Тумайкин wrote:
> Hello, Mr. Fengguang.
>
> This latter patch fixed the problem completely! I've tested vanilla 3.2 with both patches applied and with only the latter one, results are the same:
> - first of all the initial problem solved. I have no "divide error" (not sure if this panic) now.
> - doing daily desktop stuff (e.g. web browsing, movie playback, book reading etc) also without any errors as well as compiling packages.
>
> So, I can confirm the problem is solved completely.
> Thank you and your colleagues very much for you fast response and active help! I am very grateful!
Ilya, thank you too for your report and testing! I'll submit the patch right now.
Thanks,
Fengguang
> --- Пн, 9.1.12, Wu Fengguang <wfg@linux.intel.com> пишет:
>
> > От: Wu Fengguang <wfg@linux.intel.com>
> > Тема: Re: A regression in recent 3.2 kernel: bdi_dirty_limit() divide error
> > Кому: "Peter Zijlstra" <a.p.zijlstra@chello.nl>
> > Копия: "Илья Тумайкин" <librarian_rus@yahoo.com>, "LKML" <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org
> > Дата: Понедельник, 9 январь 2012, 7:04
> > On Sun, Jan 08, 2012 at 11:19:14AM
> > +0100, Peter Zijlstra wrote:
> >
> > > But even then, we limit PROP_MAX_SHIFT to
> > 3*BITS_PER_LONG/4, I don't
> > > think that could ever overflow.
> >
> > do_div() only uses the lower 32 bit value of the 64 bit
> > denominator,
> > which may happen to be 0.
> >
> > The denominator is not really 64 bit, but limited by
> > PROP_MAX_SHIFT =
> > 48 bit, however that upper limit looks not enough.
> >
> > Ilya, would you help try the attached patch instead?
> >
> > Thanks,
> > Fengguang
> >
next prev parent reply other threads:[~2012-01-10 14:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1325884395.57034.YahooMailClassic@web161605.mail.bf1.yahoo.com>
2012-01-07 14:56 ` A regression in recent 3.2 kernel: bdi_dirty_limit() divide error Wu Fengguang
2012-01-07 16:35 ` Peter Zijlstra
2012-01-08 2:33 ` Wu Fengguang
2012-01-08 10:19 ` Peter Zijlstra
2012-01-09 4:04 ` Wu Fengguang
[not found] ` <1326205945.62365.YahooMailClassic@web161603.mail.bf1.yahoo.com>
2012-01-10 14:38 ` Wu Fengguang [this message]
2012-01-10 14:38 ` Wu Fengguang
2012-01-09 4:55 ` Wu Fengguang
2012-01-10 14:54 ` [PATCH] lib: proportion: lower PROP_MAX_SHIFT to 32 on 64-bit kernel Wu Fengguang
2012-01-10 15:01 ` Wu Fengguang
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