[libvirt] Attempting to pivot disk with incomplete mirror results in hang

[Scott Sullivan]

On 01/13/2015 03:05 PM, Eric Blake wrote:
> On 01/13/2015 12:43 PM, Scott Sullivan wrote:
>> I have what appears to be a bug when pivoting a disk during a block copy that is not yet 100% finished, resulting in the pivot command hanging. I have verified this problem on libvirt 1.2.10.
> Known issue:
> https://bugzilla.redhat.com/show_bug.cgi?id=1134294
>
>> Here's what Im seeing (transient guest):
>>
>> 1.) Start the block copy:
>>
>> [root at host ~]# virsh blockcopy f20-SPICE vda /dev/sdc --format=raw --blockdev
>> Block Copy started
>> [root at host ~]#
>>
>> 2.) Query status to see it works/is started
>>
>> [root at host ~]# virsh blockjob --info f20-SPICE vda
>> Block Copy: [  1 %]
>>
>> [root at host ~]#
>>
>> 3.) Attempt the pivot before mirror reaches 100% (this makes cmd hang)
>>
>> [root at test-parent-kvm ~]# virsh blockjob f20-SPICE vda --pivot
>> ^^^ cmd is now hanging
> The attempt to pivot should have failed immediately.  I'm working on a
> patch.
>
>> -------------------------------------------------------------
>>
>> When its hanging, I see this in /var/log/libvirt/libvirtd.log
>>
>> 19:29:33.376+0000: 1845: error : qemuDomainBlockPivot:15367 : block copy still active: disk 'vda' not ready for pivot yet
>> 19:30:31.000+0000: 1842: warning : qemuDomainObjBeginJobInternal:1376 : Cannot start job (query, none) for domain f20-SPICE; current job is (modify, none) owned by (1845, 0)
>> 19:30:31.000+0000: 1842: error : qemuDomainObjBeginJobInternal:1381 : Timed out during operation: cannot acquire state change lock
>>
>> This then makes other commands querying this domain hang as well, such as:
>>
>> virsh blockjob --info f20-SPICE vda
>>
>> With this being put into log:
>>
>> 19:30:31.000+0000: 1842: error : qemuDomainObjBeginJobInternal:1381 : Timed out during operation: cannot acquire state change lock
>> 19:34:45.568+0000: 1841: error : virNetSocketReadWire:1571 : End of file while reading data: Input/output error
>>
>> Is this expected behavior? It would be nice if on step #3 instead of hanging the command returned in an error state saying cannot pivot because the mirror is not yet 100% or similar. I am happy to test later versions or patches as needed.
> I'll remember to cc you on the patch I post, hopefully later today :)

Excellent! I will be sure to test it. Likely will be tomorrow morning I will test it if you get one in later today. Thanks for your hard work.

>