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

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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: [email protected] [mailto:[email protected]] On Behalf Of Jeff Zheng 
Sent: Thursday, 17 May 2007 5:39 p.m.
To: Neil Brown; [email protected]; Michal Piotrowski; Ingo Molnar; [email protected]; [email protected]; [email protected] 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:[email protected]]
Sent: Thursday, 17 May 2007 5:31 p.m.
To: [email protected]; Jeff Zheng; Michal Piotrowski; Ingo Molnar; [email protected]; [email protected]; [email protected] Subject: RE: Software raid0 will crash the file-system,
when each disk 
is 5TB

On Thursday May 17, [email protected] 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 <[email protected]>

### 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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