Bug#604457: linux-image-2.6.26-2-xen-686: Raid10 exporting LV to xen results in error "can't convert block across chunks or bigger than 64k"

[Neil Brown <neilb@suse.de>]

On Sun, 28 Nov 2010 04:18:25 +0000 Ben Hutchings <benh@debian.org> wrote:

> On Sun, 2010-11-28 at 08:28 +1100, Neil Brown wrote:
> >  The fix I would recommend for 2.6.26 is to add
> > 
> >    if (q->merge_bvec_fn)
> >            rs->max_phys_segments = 1;
> > 
> > to dm_set_device_limits.  Though the redhat one is probably adequate.
> > 
> > If you really need an upstream fix, you will need to chase upstream to apply
> > one :-(
> 
> I won't do that myself - as you can see, I don't really understand the
> issue fully.  Is that fix also valid (modulo renaming of
> max_phys_segments) for later versions?
> 

Yes.
For current mainline it would look like replacing


	if (q->merge_bvec_fn && !ti->type->merge)
		limits->max_sectors =
			min_not_zero(limits->max_sectors,
				     (unsigned int) (PAGE_SIZE >> 9));

with

	if (q->merge_bvec_fn && !ti->type->merge)
		limits->max_segments = 1;

(the test on ->type->merge is important and applies to 2.6.26 as well).

NeilBrown

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