qemu: hotplug: Transfer ownership of backing chain to block job on disk unplug

When removing the disk fronted while any block job is still active we
need to transfer the ownership of the backing chain to the job itself as
the job still holds the reference to the chain members and thus attempts
to remove them would fail.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_hotplug.c

@@ -4228,8 +4228,15 @@ qemuDomainRemoveDiskDevice(virQEMUDriverPtr driver,
         if (VIR_STRDUP(corAlias, diskPriv->nodeCopyOnRead) < 0)
             goto cleanup;
 
-        if (!(diskBackend = qemuBlockStorageSourceChainDetachPrepareBlockdev(disk->src)))
-            goto cleanup;
+        if (diskPriv->blockjob) {
+            /* the block job keeps reference to the disk chain */
+            diskPriv->blockjob->disk = NULL;
+            virObjectUnref(diskPriv->blockjob);
+            diskPriv->blockjob = NULL;
+        } else {
+            if (!(diskBackend = qemuBlockStorageSourceChainDetachPrepareBlockdev(disk->src)))
+                goto cleanup;
+        }
     } else {
         char *driveAlias;
 
@@ -4252,7 +4259,8 @@ qemuDomainRemoveDiskDevice(virQEMUDriverPtr driver,
     if (corAlias)
         ignore_value(qemuMonitorDelObject(priv->mon, corAlias));
 
-    qemuBlockStorageSourceChainDetach(priv->mon, diskBackend);
+    if (diskBackend)
+        qemuBlockStorageSourceChainDetach(priv->mon, diskBackend);
 
     if (qemuDomainObjExitMonitor(driver, vm) < 0)
         goto cleanup;
@@ -4262,7 +4270,8 @@ qemuDomainRemoveDiskDevice(virQEMUDriverPtr driver,
     qemuDomainReleaseDeviceAddress(vm, &disk->info);
 
     /* tear down disk security access */
-    qemuDomainStorageSourceChainAccessRevoke(driver, vm, disk->src);
+    if (diskBackend)
+        qemuDomainStorageSourceChainAccessRevoke(driver, vm, disk->src);
 
     dev.type = VIR_DOMAIN_DEVICE_DISK;
     dev.data.disk = disk;