[linux-lvm] [PATCH 01/10] lvchange: Allow cluster lock conversion

[Vladislav Bogdanov]

19.03.2013 18:23, David Teigland wrote:
> On Tue, Mar 19, 2013 at 01:32:41PM +0000, Vladislav Bogdanov wrote:
>> Allow clvm locks to be converted shared <-> exclusive with corosync/dlm.
>>
>> Without this it is impossible to alow both
>> * VM migration (shared lock is required)
>> * host-side snapshots of VM disks (exlusive lock is required)
>>
>> Locks are only converted if --force parameter passed to lvchange.
>>
>> Internally LKF_CONVERT flag is passed to dlm, so that is a real lock
>> conversion.
>>
>> Also deny release of an exclusive lock on a remote note without --force
>> flag to lvchange -an.
> 
> I'm trying to figure out why the code doesn't already use CONVERT when
> possible; I would have expected it to. 

Like me - that's why this patch.

> (It has to be combined with
> NOQUEUE to avoid deadlocks.)

It is from what I see.

> What happens now without this force/CONVERT
> patch? a new lock created/requested?
> 

No, just returns error.

...
#lvchange.c:153     Activating logical volume "lustre03-right.vds-ok.com_disk0" exclusively
#activate/dev_manager.c:285         Getting device info for VG_VDS_OK_POOL_1-lustre03--right.vds--ok.com_disk0 [LVM-2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O]
#ioctl/libdm-iface.c:1687         dm info  LVM-2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O NF   [16384] (*1)
#locking/cluster_locking.c:563         Lock held for 2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O, node 3804050a : CR
#locking/cluster_locking.c:563         Lock held for 2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O, node 5c04050a : CR
#locking/cluster_locking.c:563         Lock held for 2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O, node 3904050a : CR
#activate/activate.c:1050       VG_VDS_OK_POOL_1/lustre03-right.vds-ok.com_disk0 is active
#locking/cluster_locking.c:503       Locking LV 2nCt35tXpJcEJUErLzSM3nTjJZwr0DvX3FDOuTp381ZIEVQvUrGCqoSYs4lGhW2O EX (LV|NONBLOCK|CLUSTER|LOCAL) (0xdd)
#locking/cluster_locking.c:391   Error locking on node 3904050a: Device or resource busy
...