ARM/kirkwood: v3.12-rc6: kernel BUG at mm/util.c:390!

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 [off-list ref] wrote:

quoted

On Thu, Oct 24, 2013 at 09:07:30PM +0100, Aaro Koskinen wrote:

quoted

[   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 [off-list ref]
Date:   Mon Jun 10 21:10:12 2013 +0100

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

A.