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Not 100% reproducible. 

dmeventd was running while lvcreate was attempted

So far I was not able to reproduce manually because of bug's random behaviour so I can not attach the verbose logs.

lvm2-2.02.177-1.el7.x86_64

[2018-02-08 11:20:44.683431] SCENARIO - [triple_dmeventd_monitoring]
[2018-02-08 11:20:44.683751] Turn dmeventd monitoring on for mirror, snapshot and thin
[2018-02-08 11:20:44.684043] Have dmeventd monitoring turned on for a:
[2018-02-08 11:20:44.684305] 	mirror (libdevmapper-event-lvm2mirror.so)
[2018-02-08 11:20:44.684566] 	snapshot (libdevmapper-event-lvm2snapshot.so)
[2018-02-08 11:20:44.684782] 	thin (libdevmapper-event-lvm2thin.so)
[2018-02-08 11:20:44.685001] Make a couple mirrored with snapshot volumes
[2018-02-08 11:20:44.685273] lvcreate --activate ey --type mirror -m 1 -n dual_mirror_1 --alloc anywhere -L 100M snapper_thinp
[2018-02-08 11:20:44.926140]   Error locking on node UNKNOWN 1: Refusing activation of partial LV snapper_thinp/dual_mirror_1_mlog.  Use '--activationmode partial' to override.
[2018-02-08 11:20:44.926371]   Aborting. Failed to activate mirror log.
[2018-02-08 11:20:44.991836]   Failed to initialise mirror log.

This is what dm table contained after lvcreate failure. Unfortunately I can not get the tables from all nodes since I'm not able to reproduce this after reboot.

# dmsetup table
rhel_virt--369-swap: 0 1679360 linear 252:2 2048
rhel_virt--369-root: 0 12992512 linear 252:2 1681408
snapper_thinp-dual_mirror_1_mlog: 0 8192 linear 8:145 16384

Created attachment 1393185 [details]
lvcreate_vvvv

I just recalled saving the log from previous attempts so here it is.

From log trace it looks like failure was cause by:

device-mapper: create ioctl on snapper_thinp-dual_mirror_1_mlog

So here lvm2 could not create a DM device with this name - likely becuase it already exists in your system.

The possibly explanation is the device has been 'forgotten' leaked from some other previous test.


So the failure is rather in the situation where this device was not removed during some 'vgremove -f' command for whatever reason.


So far I'm not seeing the bug on lvcreate side.

It works as designed - lvcreate simply stops when it find 'name collision' and it's upto admin to resolve this case.

Simplest way to trigger is the 'dmsetup' some  DM device with name in form of  'vgname-lvname'  and then run 'lvcreate' with matching name.