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

[Bill Davidsen <davidsen@tmr.com>]

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@vger.kernel.org 
> > [mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jeff Zheng
> > Sent: Thursday, 17 May 2007 5:39 p.m.
> > To: Neil Brown; david@lang.hm; Michal Piotrowski; Ingo 
> > Molnar; linux-raid@vger.kernel.org; 
> > linux-kernel@vger.kernel.org; linux-fsdevel@vger.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@suse.de]
> > > Sent: Thursday, 17 May 2007 5:31 p.m.
> > > To: david@lang.hm; Jeff Zheng; Michal Piotrowski; Ingo Molnar; 
> > > linux-raid@vger.kernel.org; linux-kernel@vger.kernel.org; 
> > > linux-fsdevel@vger.kernel.org
> > > Subject: RE: Software raid0 will crash the file-system, 
> > when each disk 
> > > is 5TB
> > >
> > > On Thursday May 17, neilb@suse.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@suse.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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--
Bill Davidsen <davidsen@tmr.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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