[libvirt] [PATCH v5 4/4] blockcommit: turn on active commit

[Eric Blake]

On 07/29/2014 07:06 AM, Peter Krempa wrote:
> On 07/29/14 06:20, Eric Blake wrote:
>> With this in place, I can (finally!) now do:
>>
>> virsh blockcommit $dom vda --shallow --verbose --pivot
>>
>> and watch qemu shorten the backing chain by one, followed by
>> libvirt automatically updating the dumpxml output, effectively
>> undoing the work of virsh snapshot-commit --no-metadata --disk-only.
>> Commit is SOOOO much faster than blockpull, when I'm still fairly
>> close in time to when the temporary qcow2 wrapper file was created
>> via a snapshot operation!
>>
>> * src/qemu/qemu_driver.c (qemuDomainBlockCommit): Implement live
>> commit.
>>
>> Signed-off-by: Eric Blake <eblake at redhat.com>
>> ---
>>  src/qemu/qemu_driver.c | 36 ++++++++++++++++++++++++++++++++----
>>  1 file changed, 32 insertions(+), 4 deletions(-)
>>
> 
> ACK,
> 
> didn't change from my previous commit much.

Alas, it needs to change - now that I'm more careful about using the
qemu events to react to state changes, I have to be prepared for a qemu
event that occurs prior to regaining lock in the main code.  I'll post a
v6, but here's the interdiff:

diff --git i/src/qemu/qemu_driver.c w/src/qemu/qemu_driver.c
index 6a649e5..c619fbb 100644
--- i/src/qemu/qemu_driver.c
+++ w/src/qemu/qemu_driver.c
@@ -15673,23 +15673,31 @@ qemuDomainBlockCommit(virDomainPtr dom,
      * if any, through to qemu, since qemu may behave differently
      * depending on whether the input was specified as relative or
      * absolute (that is, our absolute top_canon may do the wrong
-     * thing if the user specified a relative name). */
+     * thing if the user specified a relative name).  Be prepared for
+     * a ready event to occur while locks are dropped.  */
+    if (mirror) {
+        disk->mirror = mirror;
+        disk->mirrorJob = VIR_DOMAIN_BLOCK_JOB_TYPE_ACTIVE_COMMIT;
+    }
     qemuDomainObjEnterMonitor(driver, vm);
     ret = qemuMonitorBlockCommit(priv->mon, device,
                                  topPath, basePath, backingPath,
                                  bandwidth);
     qemuDomainObjExitMonitor(driver, vm);

-    if (ret == 0 && mirror) {
-        virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+    if (mirror) {
+        if (ret == 0) {
+            virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);

-        disk->mirror = mirror;
-        mirror = NULL;
-        disk->mirrorJob = VIR_DOMAIN_BLOCK_JOB_TYPE_ACTIVE_COMMIT;
-        if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0)
-            VIR_WARN("Unable to save status on vm %s after block job",
-                     vm->def->name);
-        virObjectUnref(cfg);
+            mirror = NULL;
+            if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0)
+                VIR_WARN("Unable to save status on vm %s after block job",
+                         vm->def->name);
+            virObjectUnref(cfg);
+        } else {
+            disk->mirror = NULL;
+            disk->mirrorJob = VIR_DOMAIN_BLOCK_JOB_TYPE_UNKNOWN;
+        }
     }

  endjob:

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

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