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

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Date:	Fri, 18 May 2007 10:55:48 +1200
From:	"Jeff Zheng" <Jeff.Zheng@...ace.com>
To:	"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

 Fix confirmed, filled the whole 11T hard disk, without crashing.
I presume this would go into 2.6.22

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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