linux-kernel - Re: Software raid0 will crash the file-system, when each disk is 5TB

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Message-ID: <46536128.50504@tmr.com>
Date:	Tue, 22 May 2007 17:31:20 -0400
From:	Bill Davidsen <davidsen@....com>
To:	Jeff Zheng <Jeff.Zheng@...ace.com>
CC:	Neil Brown <neilb@...e.de>, david@...g.hm,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Ingo Molnar <mingo@...e.hu>, linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Software raid0 will crash the file-system, when each disk is
 5TB

Jeff Zheng wrote:
>  Fix confirmed, filled the whole 11T hard disk, without crashing.
> I presume this would go into 2.6.22
> 
Since it results in a full loss of data, I would hope it goes into 
2.6.21.x -stable.

> Thanks again.
> 
> Jeff
> 
>> -----Original Message-----
>> From: linux-raid-owner@...r.kernel.org 
>> [mailto:linux-raid-owner@...r.kernel.org] On Behalf Of Jeff Zheng
>> Sent: Thursday, 17 May 2007 5:39 p.m.
>> To: Neil Brown; david@...g.hm; Michal Piotrowski; Ingo 
>> Molnar; linux-raid@...r.kernel.org; 
>> linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org
>> Subject: RE: Software raid0 will crash the file-system, when 
>> each disk is 5TB
>>
>>
>> Yeah, seems you've locked it down, :D. I've written 600GB of 
>> data now, and anything is still fine.
>> Will let it run overnight, and fill the whole 11T. I'll post 
>> the result tomorrow
>>
>> Thanks a lot though.
>>
>> Jeff 
>>
>>> -----Original Message-----
>>> From: Neil Brown [mailto:neilb@...e.de]
>>> Sent: Thursday, 17 May 2007 5:31 p.m.
>>> To: david@...g.hm; Jeff Zheng; Michal Piotrowski; Ingo Molnar; 
>>> linux-raid@...r.kernel.org; linux-kernel@...r.kernel.org; 
>>> linux-fsdevel@...r.kernel.org
>>> Subject: RE: Software raid0 will crash the file-system, 
>> when each disk 
>>> is 5TB
>>>
>>> On Thursday May 17, neilb@...e.de wrote:
>>>> Uhm, I just noticed something.
>>>> 'chunk' is unsigned long, and when it gets shifted up, we
>>> might lose
>>>> bits.  That could still happen with the 4*2.75T 
>> arrangement, but is 
>>>> much more likely in the 2*5.5T arrangement.
>>> Actually, it cannot be a problem with the 4*2.75T arrangement.
>>>   chuck << chunksize_bits
>>>
>>> will not exceed the size of the underlying device *in*kilobytes*.
>>> In that case that is 0xAE9EC800 which will git in a 32bit long.
>>> We don't double it to make sectors until after we add
>>> zone->dev_offset, which is "sector_t" and so 64bit 
>> arithmetic is used.
>>> So I'm quite certain this bug will cause exactly the problems 
>>> experienced!!
>>>
>>>> Jeff, can you try this patch?
>>> Don't bother about the other tests I mentioned, just try this one.
>>> Thanks.
>>>
>>> NeilBrown
>>>
>>>> Signed-off-by: Neil Brown <neilb@...e.de>
>>>>
>>>> ### Diffstat output
>>>>  ./drivers/md/raid0.c |    2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff .prev/drivers/md/raid0.c ./drivers/md/raid0.c
>>>> --- .prev/drivers/md/raid0.c	2007-05-17 
>>> 10:33:30.000000000 +1000
>>>> +++ ./drivers/md/raid0.c	2007-05-17 15:02:15.000000000 +1000
>>>> @@ -475,7 +475,7 @@ static int raid0_make_request (request_q
>>>>  		x = block >> chunksize_bits;
>>>>  		tmp_dev = zone->dev[sector_div(x, zone->nb_dev)];
>>>>  	}
>>>> -	rsect = (((chunk << chunksize_bits) + zone->dev_offset)<<1)
>>>> +	rsect = ((((sector_t)chunk << chunksize_bits) +
>>>> +zone->dev_offset)<<1)
>>>>  		+ sect_in_chunk;
>>>>   
>>>>  	bio->bi_bdev = tmp_dev->bdev;
>> -
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>>
> -
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> 


-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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