[dm-devel] [PATCH-RFC] Bug in dm-raid1 as used by pvmove

[Jonathan E Brassow]

It looks reasonable at first glance, but I have to think about it more. 
  Do you have a test case that I can reproduce with?

  brassow

On May 8, 2006, at 11:55 PM, Neil Brown wrote:

>
> Hi,
>  We have a report of a system oops during pvmove.
>
>  What appears to be happening is core_in_sync is being passed
>  a 'region' is which much too large.  When this is indexed into the
>  bitset at lc->sync_bits it hits an unmapped page, and results in an
>  oops.
>
>  I believe the problem is in bio_to_region.  See the patch below.
>
>  If a section of an lv which is *not* at the start of the lv is being
>  moved using dm-raid1, I think the region number is being calculated
>  wrongly resulting in the inappropriately large index.  We really
>  need to subtract ti->begin from bi_sector before shifting.
>
>  We will try to get this patch tested on the machine that showed the
>  fault, but I would appreciate any feedback about the patch and I am
>  still not very familiar with this code.
>
> Thanks,
> NeilBrown
>
>
>
> Signed-off-by: Neil Brown <neilb at suse.de>
>
> ### Diffstat output
>  ./drivers/md/dm-raid1.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff ./drivers/md/dm-raid1.c~current~ ./drivers/md/dm-raid1.c
> --- ./drivers/md/dm-raid1.c~current~	2006-05-09 14:47:35.000000000 
> +1000
> +++ ./drivers/md/dm-raid1.c	2006-05-09 14:47:35.000000000 +1000
> @@ -111,7 +111,7 @@ struct region {
>   */
>  static inline region_t bio_to_region(struct region_hash *rh, struct 
> bio *bio)
>  {
> -	return bio->bi_sector >> rh->region_shift;
> +	return (bio->bi_sector - rh->ms->ti->begin) >> rh->region_shift;
>  }
>
>  static inline sector_t region_to_sector(struct region_hash *rh, 
> region_t region)
>
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