[libvirt] [PATCH v4 0/5] Expose FSFreeze/FSThaw within the guest as API

[Eric Blake]

On 03/27/2014 04:21 PM, Jon Bernard wrote:
> * Tomoki Sekiyama <tomoki.sekiyama at hds.com> wrote:
>> Hello,
>>
>> This is patchset v4 to add FSFreeze/FSThaw API for custom disk snapshotting.
> 
> This patchset works for my tests.  Without pausing the guest I am able
> to quiesce all attached volumes.  Does there exists an option to create
> a snapshot of only one (or some) of the volumes attached to a particular
> instance?

Interesting question.  The virDomainSnapshotCreateXML call can quiesce a
subset of disks (namely, only the disks that were specified in the
snapshot).  But as currently designed, the FSFreeze/FSThaw API have no
way to specify a subset of disks; it is an all-or-none proposition.

Perhaps that means the API is not quite right, and that we need a
'char**disks, int ndisks' parameter pair; if 'NULL, 0', we do all disks,
if non-NULL, then we freeze only the listed set of disks (doing the same
lookup for disks as for other APIs).

I feel a bit bad that this was posted before freeze of 1.2.3, but we
don't have it in yet, which makes it harder to commit until the 1.2.4
cycle.  On the other hand, if we decide the API needs to be tweaked to
add parameters for full usability, then maybe it's a good thing we don't
have it in yet.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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