[dm-devel] During systemd/udev, device-mapper trying to work with non-LVM volumes

[Zdenek Kabelac]

Dne 28.7.2016 v 03:33 james harvey napsal(a):
> On Wed, Jul 27, 2016 at 2:49 PM, Marian Csontos <mcsontos at redhat.com> wrote:
>> On 07/23/2016 01:14 AM, james harvey wrote:
>>>
>>> If I understand what's going on here, I think device-mapper is trying
>>> to work with two volumes that don't involve LVM, causing the errors.
>>
>>
>> If I understand correctly, these volumes DO involve LVM.
>>
>> It is not LV on top of your BTRFS volumes, but your BTRFS volumes are on top
>> of LVM.
>
> I do have some BTRFS volumes on top of LVM, including my 2 root
> volumes, but my 2 boot partitions don't involve LVM.  They're raw disk
> partitions - MD RAID 1 - BTRFS.
>
> The kernel error references "table: 253:21" and "table: 253:22".
> These entries are not referred to by running dmsetup.  If these
> correspond to dm-21 and dm-22, those are the boot volumes that don't
> involve LVM at all.

This doesn't make much sense.

253:XX are all DM devices -  few lines above you say   boot partitions are 
'raw disks'  now you say dm-21 & dm-22  are boot volumes ??

LVM is volume manager - LV is DM device (maintained by lvm2 command)
There is nothing like  lvm2 device - it's always 'dm' device.

lvm2  dm device has   LVM-   prefix in UUID

In your 'dmsetup into -c' output all DM device have this prefix - so
all your DM device are lvm2  maintained devices.

>
>> Using BTRFS with thin-shapshots is not a good idea, especially, if you have
>> multiple snapshots of btrfs' underlying device active.
>>
>> Why are you usingn BTRFS on top of thin-pool?
>> BTRFS does have snapshots and IMHO you should pick either BTRFS or
>> thin-pool.
>
> I'm not using thin-snapshots, just the thin-provisioning feature.  Is

Again doesn't make sense...


> running BTRFS in that scenario still a bad situation?  Why's that?
> I'm going to be using a lot of virtual machines, which is my main
> reason for wanting thin-provisioning.

HOWTO....

>
> I'm only using btrfs snapshots.
>
>>> Is this a device-mapper bug?  A udev bug?  Something I have configured
>>> wrong?

Seems like 99.99999% wrong configuration....

>>
>> Which distribution?
>> Kernel, lvm version?
>
> Sorry for not mentioning.  Arch, kernel 4.6.4, lvm 2.02.161, device
> mapper 1.02.131, thin-pool 1.18.0
>
>> Ideally run `lvmdump -m` and post output, please.
>
> The number of kernel errors during boot that I'm getting seems to be
> random.  (Probably some type of race condition?)  My original post
> happened to be that it was using the ones not using LVM, but sometimes
> it's doing it on LVM backed volumes too.  Occasionally it gives no
> kernel errors.
>
> On this boot, I have these errors:
>
> ==========
> [    3.319387] device-mapper: table: 253:5: thin: Unable to activate
> thin device while pool is suspended
> [    3.394258] device-mapper: table: 253:6: thin: Unable to activate
> thin device while pool is suspended
> [    3.632259] device-mapper: table: 253:13: thin: Unable to activate
> thin device while pool is suspended
> [    3.698752] device-mapper: table: 253:14: thin: Unable to activate
> thin device while pool is suspended
> [    4.045282] device-mapper: table: 253:21: thin: Unable to activate
> thin device while pool is suspended
> [    4.117778] device-mapper: table: 253:22: thin: Unable to activate
> thin device while pool is suspended
> ==========
>


Completely confused about this - are you trying to operate with thin devices 
yourself with some 'dmsetup' commands ?   Eventually using 'docker' ?
Or maybe you haven configured lockless lvm2, where volumes are activated with 
locking_type==0  ?

Lvm surely doesn't try to activate thinLV from a suspended thin-pool ?

So you really need to expose sequence of command you try to execute - we do 
not have have crystal ball to reverse engineer your wrongly issued commands 
out of kernel error messages -  i.e. is it some 'lvchange/vgchange' producing 
it - then take  '-vvvv' trace out of those commands.

Also -  why do you even mix  btrfs with mdadm & lvm2??

btrfs has it's own solution for raid as well as for volume management.

Combining  'btrfs' and lvm2 snapshot is basically a 'weapon of mass 
destruction'  since  btrfs  has no idea which disk to use when multiple same 
devices with same signature appears in the system.

I'd strongly recommend to read some doc first to get familiar with basic 
bricks of your device stack.

The usage presented in tgz doesn't look like a proper use-case for lvm2 at 
all, and rather a misuse based on misunderstanding how all these technologies 
do work.

Regards

Zdenek