qemu: Properly report failed migration

Because we are polling we may detect some errors after we asked QEMU for
migration status even though they occurred before. If this happens and
QEMU reports migration completed successfully, we would happily report
the migration succeeded even though we should have cancelled it because
of the other error.

In practise it is not a big issue now but it will become a much bigger
issue once the check for storage migration status is moved inside the
loop in qemuMigrationWaitForCompletion.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_migration.c

@@ -2468,6 +2468,7 @@ qemuMigrationWaitForCompletion(virQEMUDriverPtr driver,
     qemuDomainJobInfoPtr jobInfo = priv->job.current;
     const char *job;
     int pauseReason;
+    int ret = -1;
 
     switch (priv->job.asyncJob) {
     case QEMU_ASYNC_JOB_MIGRATION_OUT:
@@ -2485,12 +2486,12 @@ qemuMigrationWaitForCompletion(virQEMUDriverPtr driver,
 
     jobInfo->type = VIR_DOMAIN_JOB_UNBOUNDED;
 
-    while (1) {
+    while (jobInfo->type == VIR_DOMAIN_JOB_UNBOUNDED) {
         /* Poll every 50ms for progress & to allow cancellation */
         struct timespec ts = { .tv_sec = 0, .tv_nsec = 50 * 1000 * 1000ull };
 
         if (qemuMigrationUpdateJobStatus(driver, vm, job, asyncJob) == -1)
-            break;
+            goto error;
 
         /* cancel migration if disk I/O error is emitted while migrating */
         if (abort_on_error &&
@@ -2498,40 +2499,37 @@ qemuMigrationWaitForCompletion(virQEMUDriverPtr driver,
             pauseReason == VIR_DOMAIN_PAUSED_IOERROR) {
             virReportError(VIR_ERR_OPERATION_FAILED,
                            _("%s: %s"), job, _("failed due to I/O error"));
-            break;
+            goto error;
         }
 
         if (dconn && virConnectIsAlive(dconn) <= 0) {
             virReportError(VIR_ERR_OPERATION_FAILED, "%s",
                            _("Lost connection to destination host"));
-            break;
+            goto error;
         }
 
-        if (jobInfo->type != VIR_DOMAIN_JOB_UNBOUNDED)
-            break;
-
-        virObjectUnlock(vm);
-
-        nanosleep(&ts, NULL);
-
-        virObjectLock(vm);
+        if (jobInfo->type == VIR_DOMAIN_JOB_UNBOUNDED) {
+            virObjectUnlock(vm);
+            nanosleep(&ts, NULL);
+            virObjectLock(vm);
+        }
     }
 
-    if (jobInfo->type == VIR_DOMAIN_JOB_COMPLETED) {
-        qemuDomainJobInfoUpdateDowntime(jobInfo);
-        VIR_FREE(priv->job.completed);
-        if (VIR_ALLOC(priv->job.completed) == 0)
-            *priv->job.completed = *jobInfo;
-        return 0;
-    } else if (jobInfo->type == VIR_DOMAIN_JOB_UNBOUNDED) {
-        /* The migration was aborted by us rather than QEMU itself so let's
-         * update the job type and notify the caller to send migrate_cancel.
-         */
+    qemuDomainJobInfoUpdateDowntime(jobInfo);
+    VIR_FREE(priv->job.completed);
+    if (VIR_ALLOC(priv->job.completed) == 0)
+        *priv->job.completed = *jobInfo;
+    return 0;
+
+ error:
+    /* Check if the migration was aborted by us rather than QEMU itself. */
+    if (jobInfo->type == VIR_DOMAIN_JOB_UNBOUNDED ||
+        jobInfo->type == VIR_DOMAIN_JOB_COMPLETED) {
+        if (jobInfo->type == VIR_DOMAIN_JOB_UNBOUNDED)
+            ret = -2;
         jobInfo->type = VIR_DOMAIN_JOB_FAILED;
-        return -2;
-    } else {
-        return -1;
     }
+    return ret;
 }