linux-kernel - Re: 2.6.19-rc1-mm1 - locks when using "dd bs=1M" from card reader

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Date:	Fri, 13 Oct 2006 15:11:11 +0200
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Andrew Morton <akpm@...l.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.19-rc1-mm1 - locks when using "dd bs=1M" from card reader

Andrew Morton wrote:
> On Thu, 12 Oct 2006 14:18:04 +0200
> Helge Hafting <helge.hafting@...el.hist.no> wrote:
>
>   
>> I found an easy way to hang the kernel when copying a SD-card:
>>
>> dd if=/dev/sdc of=file bs=1048576
>>
>> I.e. copy the entire 256MB card in 1MB chunks.  I got about
>> 160MB before the kernel hung.  Not even sysrq+B worked, I needed
>> the reset button.  The pc has a total of 512MB memory if that matters.
>>
>> Using bs=4096 instead let me copy the entire card with no problems,
>> but that seems to progress slower.
>>
>> The above 'dd' command hangs my office pc every time. So I can repeat
>> it for debugging purposes. 
>>
>>     
>
> What device driver is providing /dev/sdc?
>   
It is an usb card reader, so it is "usb mass storage"
and "scsi disk".
> Did any previous kernels work correctly?  If so, which?
>   

I just got that card reader, so I haven't tested any earlier kernels.
I have another machine with a card reader, which I have used for
a long time. But I only ever copy files with "cp" on that one.

This time I used "dd" to get an image of the entire card, and got trouble
when using 1M chunks. 

I can try with verbose scsi debug messages if that might help?

Helge Hafting


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