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Date: Sun, 27 Oct 2013 14:50:36 +0200
From: Aaro Koskinen <aaro.koskinen@iki.fi>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>, gmbnomis@gmail.com,
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        FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
        Tejun Heo <tj@kernel.org>,
        "James E.J. Bottomley" <JBottomley@parallels.com>,
        Jens Axboe <axboe@kernel.dk>
Subject: Re: ARM/kirkwood: v3.12-rc6: kernel BUG at mm/util.c:390!
Message-ID: <20131027125036.GJ17447@blackmetal.musicnaut.iki.fi>
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Hi,

On Sun, Oct 27, 2013 at 07:51:15PM +0800, Ming Lei wrote:
> On Sat, 26 Oct 2013 15:36:17 +0100
> Will Deacon <will.deacon@arm.com> wrote:
> 
> > On Thu, Oct 24, 2013 at 09:07:30PM +0100, Aaro Koskinen wrote:
> > 
> > > [   36.477203] Backtrace:
> > > [   36.535603] [<c009237c>] (page_mapping+0x0/0x50) from [<c0010dd8>] (flush_kernel_dcache_page+0x14/0x98)
> > > [   36.661070] [<c0010dc4>] (flush_kernel_dcache_page+0x0/0x98) from [<c0172b60>] (sg_miter_stop+0xc8/0x10c)
> > > [   36.792813]  r4:df8a9a64 r3:00000003
> > > [   36.857524] [<c0172a98>] (sg_miter_stop+0x0/0x10c) from [<c0172f20>] (sg_miter_next+0x14/0x13c)
> > 
> > ... assumedly for scatter/gather DMA. How is your block driver allocating
> > its buffers? If you're using the DMA API, I can't see how this would happen.
> 
> Lots of SCSI commands(inquiry, ...) pass kmalloc buffer to block layer,
> then the sg buffer copy helpers and flush_kernel_dcache_page() may see
> slab page.
> 
> That has been here from commit b1adaf65ba03( [SCSI] block: add sg buffer copy
> helper functions).

On ARM v3.9 or older kernels do not trigger this BUG, at seems it only
started to appear with the following commit (bisected):

commit 1bc39742aab09248169ef9d3727c9def3528b3f3
Author: Simon Baatz <gmbnomis@gmail.com>
Date:   Mon Jun 10 21:10:12 2013 +0100

    ARM: 7755/1: handle user space mapped pages in flush_kernel_dcache_page

A.
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