[PATCH 22/33] migration: push Error **errp into qemu_savevm_state_iterate()

["Daniel P. Berrangé" <berrange@redhat.com>]

This is an incremental step in converting vmstate loading code to report
via Error objects instead of printing directly to the console/monitor.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 migration/migration.c |  8 +++++++-
 migration/savevm.c    | 47 ++++++++++++++++++++++++++-----------------
 migration/savevm.h    |  2 +-
 3 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 395a1b10f5..a85d101ad8 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3393,6 +3393,8 @@ static MigIterateState migration_iteration_run(MigrationState *s)
                           pend_pre, pend_compat, pend_post);
 
     if (pending_size && pending_size >= s->threshold_size) {
+        int ret;
+        Error *local_err = NULL;
         /* Still a significant amount to transfer */
         if (!in_postcopy && pend_pre <= s->threshold_size &&
             qatomic_read(&s->start_postcopy)) {
@@ -3402,7 +3404,11 @@ static MigIterateState migration_iteration_run(MigrationState *s)
             return MIG_ITERATE_SKIP;
         }
         /* Just another iteration step */
-        qemu_savevm_state_iterate(s->to_dst_file, in_postcopy);
+        ret = qemu_savevm_state_iterate(s->to_dst_file, in_postcopy,
+                                        &local_err);
+        if (ret < 0) {
+            error_report_err(local_err);
+        }
     } else {
         trace_migration_thread_low_pending(pending_size);
         migration_completion(s);
diff --git a/migration/savevm.c b/migration/savevm.c
index 6a7b930b1c..23e4d5a1a2 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1220,8 +1220,9 @@ int qemu_savevm_state_resume_prepare(MigrationState *s)
  *   negative: there was one error, and we have -errno.
  *   0 : We haven't finished, caller have to go again
  *   1 : We have finished, we can go to complete phase
+ *  -1 : error reported, go to cleanup phase
  */
-int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
+int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy, Error **errp)
 {
     SaveStateEntry *se;
     int ret = 1;
@@ -1261,11 +1262,13 @@ int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
         save_section_footer(f, se);
 
         if (ret < 0) {
-            error_report("failed to save SaveStateEntry with id(name): %d(%s)",
-                         se->section_id, se->idstr);
+            error_setg(errp,
+                       "failed to save SaveStateEntry with id(name): %d(%s)",
+                       se->section_id, se->idstr);
             qemu_file_set_error(f, ret);
+            return -1;
         }
-        if (ret <= 0) {
+        if (ret == 0) {
             /* Do not proceed to the next vmstate before this one reported
                completion of the current stage. This serializes the migration
                and reduces the probability that a faster changing state is
@@ -1517,7 +1520,6 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
 {
     int ret;
     MigrationState *ms = migrate_get_current();
-    MigrationStatus status;
 
     if (migration_is_running(ms->state)) {
         error_setg(errp, QERR_MIGRATION_ACTIVE);
@@ -1538,34 +1540,43 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     qemu_savevm_state_setup(f);
     qemu_mutex_lock_iothread();
 
-    while (qemu_file_get_error(f) == 0) {
-        if (qemu_savevm_state_iterate(f, false) > 0) {
+    while (1) {
+        ret = qemu_savevm_state_iterate(f, false, errp);
+        if (ret < 0) {
+            goto fail;
+        }
+        if (ret > 0) {
             break;
         }
+        ret = qemu_file_get_error(f);
+        if (ret != 0) {
+            error_setg_errno(errp, -ret, "Error while writing VM state");
+            goto fail;
+        }
     }
 
+    qemu_savevm_state_complete_precopy(f, false, false);
     ret = qemu_file_get_error(f);
-    if (ret == 0) {
-        qemu_savevm_state_complete_precopy(f, false, false);
-        ret = qemu_file_get_error(f);
-    }
-    qemu_savevm_state_cleanup();
     if (ret != 0) {
         error_setg_errno(errp, -ret, "Error while writing VM state");
+        goto fail;
     }
 
-    if (ret != 0) {
-        status = MIGRATION_STATUS_FAILED;
-    } else {
-        status = MIGRATION_STATUS_COMPLETED;
-    }
-    migrate_set_state(&ms->state, MIGRATION_STATUS_SETUP, status);
+    qemu_savevm_state_cleanup();
+    migrate_set_state(&ms->state, MIGRATION_STATUS_SETUP,
+                      MIGRATION_STATUS_COMPLETED);
 
     /* f is outer parameter, it should not stay in global migration state after
      * this function finished */
     ms->to_dst_file = NULL;
 
     return ret;
+
+ fail:
+    qemu_savevm_state_cleanup();
+    migrate_set_state(&ms->state, MIGRATION_STATUS_SETUP,
+                      MIGRATION_STATUS_FAILED);
+    return -1;
 }
 
 void qemu_savevm_live_state(QEMUFile *f)
diff --git a/migration/savevm.h b/migration/savevm.h
index 1cec83c729..e187640806 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -34,7 +34,7 @@ void qemu_savevm_state_setup(QEMUFile *f);
 bool qemu_savevm_state_guest_unplug_pending(void);
 int qemu_savevm_state_resume_prepare(MigrationState *s);
 void qemu_savevm_state_header(QEMUFile *f);
-int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy);
+int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy, Error **errp);
 void qemu_savevm_state_cleanup(void);
 void qemu_savevm_state_complete_postcopy(QEMUFile *f);
 int qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only,
-- 
2.29.2