[libvirt] [PATCHv3 08/43] snapshot: avoid crash when deleting qemu snapshots

[Eric Blake]

On 08/24/2011 10:38 AM, Daniel P. Berrange wrote:
> On Wed, Aug 24, 2011 at 09:22:25AM -0600, Eric Blake wrote:
>> This one's nasty.  Ever since we fixed virHashForEach to prevent
>> nested hash iterations for safety reasons, virDomainSnapshotDelete
>> with VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN has been broken for qemu:
>> it deletes children, while leaving grandchildren intact but pointing
>> to a no-longer-present parent.  But even before then, the code would
>> often appear to succeed to clean up grandchildren, but risked memory
>> corruption if you have a large and deep hierarchy of snapshots.
>>
> I also still saw errors in libvirtd logs
>
> 17:36:36.175: 4423: info : libvirt version: 0.9.4
> 17:36:36.175: 4423: error : virHashSearch:604 : Hash operation not allowed during iteration
> 17:36:36.176: 4423: warning : virDomainSnapshotMarkDescendant:11309 : snapshot hash table is inconsistent!

Ouch; I can reproduce.  I guess I didn't test this one as thoroughly as 
I had planned, and this is indeed a bug in my 'forEachDescendant' 
iterator.  I'll post an update once I figure out where I went wrong.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org