[libvirt] [PATCH v2 10/12] getstats: add new flag for block backing chain
Eric Blake
eblake at redhat.com
Wed Dec 17 08:32:57 UTC 2014
On 12/16/2014 08:11 AM, Peter Krempa wrote:
> On 12/16/14 09:04, Eric Blake wrote:
>> This patch introduces access to allocation information about
>> a backing chain of a live domain. While querying storage
>> volumes for read-only disks could provide some of the details,
>> there is one case where we have to rely on qemu: when doing
>> a block commit into a backing file, where that file is stored
>> in qcow2 format on a host block device, we want to know the
>> current highest write offset into that image, in order to know
>> if the disk must be resized larger. qemu-img does not
>> (currently) show this information, and none of the earlier
>> block APIs were extensible enough to expose it. But
>> virDomainListGetStats is perfect for the job!
>>
>> * block device.
>> + * "block.<num>.backingIndex" - unsigned int giving the <backingStore> index,
>> + * when backing images are listed.
>
> You add the field to this help, but ...
>
>> -I<--block> returns:
>> +I<--block> returns information about disks associated with each
>> +domain. Using the I<--backing> flag extends this information to
>> +cover all resources in the backing chain, rather than the default
>> +of limiting information to the active layer for each guest disk.
>> +Information listed includes:
>> "block.count" - number of block devices on this domain,
>> "block.<num>.name" - name of the target of the block device <num>,
>> "block.<num>.path" - file source of block device <num>, if it is a
>>
>
> ... not to the manpage.
>
> ACK with ^^.
Fixed and pushed.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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