Bug#684712: lvm2: automatically filter imsm and ddf formatted disks

[Miquel van Smoorenburg]

On 08/14/2012 11:38 PM, Alasdair G Kergon wrote:
> On Mon, Aug 13, 2012 at 12:25:04PM +0200, Miquel van Smoorenburg wrote:
>> This patch makes sure that disks with signatures of one of these
>> metadata formats are also filtered out. To minimize the chance of
>> regressions, it only does this if md is actually running (i.e.
>> /proc/mdstat is present).
>
> Why is /proc/mdstat relevant?
>
> Do the signatures not appear without it?
> Otherwise that check shouldn't be added.

I was just being cautious. In theory, it could be that someone has 
re-used a disk that had a ddf or imsm signature, and if nothing has 
overwritten that signature in the mean time such a setup might now break 
with lvm. Unless ofcourse md raid was activated, in which case mdadm in 
initrd would have triggered on it (in debian, mdadm is started before 
lvm) and would have broken the system in a different way..

OTOH, mdadm had the same theoretical issue when it started to support 
imsm/ddf and apparently that worked out ok, so probably that check 
should be dropped.

> And I'm not sure that it's exclusively 'md' (dmraid?) so the code might
> need to go in a function with a different name.

I guess. What about the attached patch? The only thing is that I did not 
bother to create seperate ddf_component_detection and 
imsm_component_detection settings in lvm.conf, for now that's all lumped 
under the md_component_detection setting.


Thanks,

Mike.
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