[libvirt] [PATCH 2/3] snapshots: Introduce VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE flag

[Michal Privoznik]

On 24.01.2012 19:49, Jiri Denemark wrote:
> On Tue, Jan 24, 2012 at 18:37:44 +0100, Michal Privoznik wrote:
>> With this flag, virDomainSnapshotCreate will use fs-freeze and
>> fs-thaw guest agent commands to quiesce guest's disks.
>> ---
>>  include/libvirt/libvirt.h.in |    4 ++
>>  src/libvirt.c                |    6 ++
>>  src/qemu/qemu_driver.c       |  118 ++++++++++++++++++++++++++++++++++++-----
>>  3 files changed, 113 insertions(+), 15 deletions(-)
>>
>> diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
>> index 5e6e488..182065d 100644
>> --- a/include/libvirt/libvirt.h.in
>> +++ b/include/libvirt/libvirt.h.in
>> @@ -3125,6 +3125,10 @@ typedef enum {
>>                                                            system checkpoint */
>>      VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT   = (1 << 5), /* reuse any existing
>>                                                            external files */
>> +    VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE     = (1 << 6), /* use guest agent to
>> +                                                          quiesce all mounted
>> +                                                          file systems within
>> +                                                          the domain */
> 
> Do we also want to add another flag that would make quiescing optional? That
> is, use it if it's available but don't fail if it's not.

If this is ever needed we can add it then.

>> @@ -9493,6 +9543,13 @@ qemuDomainSnapshotCreateActive(virConnectPtr conn,
>>      }
>>  
>>      if (virDomainObjGetState(vm, NULL) == VIR_DOMAIN_RUNNING) {
>> +        if ((flags & VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE) &&
>> +            (qemuDomainSnapshotFSFreeze(driver, vm) < 0)) {
>> +            qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                            _("Unable to freeze domain's file systems"));
> 
> This just masks useful error reported by qemuDomainSnapshotFSFreeze().

In fact, I just realized, this is dead code. Since we are checking for
DISK_ONLY flag which implies calling
qemuDomainSnapshotCreateDiskActive() we will never get this condition to
evaluate as true. I'll drop it in v2.