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

Jeff Zheng
2007-05-17T05:39:16Z

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;
>