[linux-lvm] unable to remove snapshot of raid1 leg

[Alexander 'Leo' Bergolth]

On 10/23/2017 04:44 PM, Heinz Mauelshagen wrote:
> LVM snapshots are meant to be used on the user visible raid1 LVs.
> You found a bug allowing it to be used on its hidden legs.
> 
> Removing such per leg snapshot should be possible after the raid1 LV got
> deactivated.

Hmm. This LV is currently in use. Any chance to remove it with the raid1
LV active?

Cheers,
--leo

> On 10/23/2017 04:19 PM, Alexander 'Leo' Bergolth wrote:
>> Hi!
>>
>> As the raid1 check of my two-drive LV recently reported a mismatch count
>>> 0, I did some forensics.
>> One experiment was to create a snapshot of one leg of the mirror and try
>> to mount the snapshot. This worked fine but unfortunately I cannot
>> remove the snapshot now!
>>
>> lvm wants to remove the origin too:
>> -------------------- 8< --------------------
>> # lvremove vg_test/snap_leg_0
>> Do you really want to remove active origin logical volume
>> vg_test/testlv_rimage_0 with 1 snapshot(s)? [y/n]: n
>>    Logical volume vg_test/testlv_rimage_0 not removed.
>> -------------------- 8< --------------------
>> (I have added the full history of a test setup below.)
>>
>> Could anyone provide a hint how to get rid of the snapshot?
>> (Maybe manually using dmsetup commands and metadata backup editing?)
>>
>> Thanks,
>> --leo
>>
>> -------------------- snip! --------------------
>> # lvcreate --type raid1 -m 1 -n testlv -L100m vg_test /dev/vdb /dev/vdc
>>    Logical volume "testlv" created.
>> # lvcreate -s -L50m -n snap_leg_0 /dev/mapper/vg_test-testlv_rimage_0
>>    Using default stripesize 64.00 KiB.
>>    Rounding up size to full physical extent 52.00 MiB
>>    Logical volume "snap_leg_0" created.
>>
>> # lvremove vg_test/snap_leg_0
>> Do you really want to remove active origin logical volume
>> vg_test/testlv_rimage_0 with 1 snapshot(s)? [y/n]: n
>>    Logical volume vg_test/testlv_rimage_0 not removed.
>>
>> # lvs -a -o+devices,lv_uuid
>>    LV                VG      Attr       LSize   Pool Origin           
>> Data%  Meta%  Move Log Cpy%Sync Convert
>> Devices                               LV UUID
>>    root              vg_sys  -wi-ao----  
>> 5.00g                                                               
>> /dev/vda2(0)                         
>> fqp4Np-mLyL-y0OS-nufS-0hsT-7ijc-lGD9Za
>>    swap              vg_sys  -wi-ao----  
>> 2.00g                                                               
>> /dev/vda2(2048)                      
>> uNG1ht-eOKQ-y8Ji-yWSU-ZkZS-ZTIe-1M82mW
>>    var               vg_sys  -wi-ao----  
>> 3.00g                                                               
>> /dev/vda2(1280)                      
>> nDwCsP-vn38-6AUb-Dqer-VkLv-QHs3-CfVNCR
>>    snap_leg_0        vg_test swi-a-s---  52.00m      [testlv_rimage_0]
>> 0.00                                   
>> /dev/vdb(26)                         
>> f5AXqK-lDNe-hNrO-AW7G-yFvl-ctxU-fivKQf
>>    testlv            vg_test rwi-a-r---
>> 100.00m                                               100.00          
>> testlv_rimage_0(0),testlv_rimage_1(0)
>> Av5Y8Z-NBTH-tfN2-hCbW-Sur0-ebGU-SHBlsk
>>    [testlv_rimage_0] vg_test owi-aor---
>> 100.00m                                                               
>> /dev/vdb(1)                          
>> OJyEep-Lgfm-B20o-4rfl-d38O-QByz-8oBa5z
>>    [testlv_rimage_1] vg_test iwi-aor---
>> 100.00m                                                               
>> /dev/vdc(1)                          
>> J4AP4p-Mhfo-4oPn-SOFP-CGAi-riyL-CFr1fk
>>    [testlv_rmeta_0]  vg_test ewi-aor---  
>> 4.00m                                                               
>> /dev/vdb(0)                          
>> Hgd58x-5Z2C-phkD-cIvl-KbPB-UWPz-THyZ3h
>>    [testlv_rmeta_1]  vg_test ewi-aor---  
>> 4.00m                                                               
>> /dev/vdc(0)                          
>> mvehrT-Ofci-nWpm-A43m-iBpl-YW1U-Z1Z9x4
>>
>> # lvremove --select lv_uuid=f5AXqK-lDNe-hNrO-AW7G-yFvl-ctxU-fivKQf
>> Do you really want to remove active origin logical volume
>> vg_test/testlv_rimage_0 with 1 snapshot(s)? [y/n]: n
>>    Logical volume vg_test/testlv_rimage_0 not removed.
>> -------------------- snip! --------------------
>>
>>
> 


-- 
e-mail   ::: Leo.Bergolth (at) wu.ac.at
fax      ::: +43-1-31336-906050
location ::: IT-Services | Vienna University of Economics | Austria