Internal error: Pool read_vg crc mismatch only when running in test environment

[Tony Asleson <tasleson@redhat.com>]

On 06/21/2013 08:53 AM, Zdenek Kabelac wrote:
> Dne 21.6.2013 01:18, Tony Asleson napsal(a):
>> Writing some new unit test cases for my latest liblvm patch set and at
>> the moment I am running into a case where I can run the unit test case
>> against real disk and it works, but if I run it in the test environment
>> with loop back devices I am getting an abort with:
>>
>> "Internal error: Pool read_vg crc mismatch."
>>
>> Any ideas why this error isn't occurring on both?
>>
> 
> This happens - if you have requested 'read-only'  VG struct,
> and you have modifed something in this vgmem pool
> (either writing to struct, or just using vgmem pool for allocation)

My original inquiry was for ideas why I see this on loop back devices
and not actual devices.  This response doesn't seem to match what I am
seeing.

The stack trace shows that we are getting this error during an
lvm_vg_open.  I can re-create the error regardless if I open the vg
struct as read-only or read-write.

>From my initial debug it appears that if the vginfo->vg_use_count > 1
(in this case 3) we pass 1 as the second parameter to dm_pool_unlock
which is a crc check of the pool which it finds to be different.  At
this point it would seem I am exacerbating some type of caching bug or
that somewhere along the path I am inadvertently changing the contents
of the vg struct pointer with my latest patches.

Regards,
Tony