migration: Refactor migration_completion_precopy() to return bool

migration_completion_precopy() reports its error through the Error
**errp argument, so its int return value carries no information beyond
success/failure. Convert it to return a bool, matching the common
convention.

Convert its underlying helper qemu_savevm_state_complete_precopy()
likewise, and in turn qemu_savevm_state_non_iterable(), which it calls.
Adjust all callers accordingly.

Refactor and clean migration_completion() code too, which no longer
needs to track int return values.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260706085211.13905-16-avihaih@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

migration/migration.c

@@ -2659,8 +2659,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
      */
     qemu_savevm_send_postcopy_listen(fb);
 
-    ret = qemu_savevm_state_non_iterable(fb, errp);
+    if (!qemu_savevm_state_non_iterable(fb, errp)) {
-    if (ret) {
         error_prepend(errp, "Postcopy save non-iterable states failed: ");
         goto fail_closefb;
     }
@@ -2858,22 +2857,22 @@ static bool migration_switchover_start(MigrationState *s, Error **errp)
     return true;
 }
 
-static int migration_completion_precopy(MigrationState *s, Error **errp)
+static bool migration_completion_precopy(MigrationState *s, Error **errp)
 {
-    int ret;
+    bool ret = false;
 
     bql_lock();
 
     if (!migrate_mode_is_cpr()) {
-        ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
+        int r = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
-        if (ret < 0) {
+
-            error_setg_errno(errp, -ret, "Failed to stop the VM");
+        if (r < 0) {
+            error_setg_errno(errp, -r, "Failed to stop the VM");
             goto out_unlock;
         }
     }
 
     if (!migration_switchover_start(s, errp)) {
-        ret = -EFAULT;
         goto out_unlock;
     }
 
@@ -2910,18 +2909,17 @@ static void migration_completion_postcopy(MigrationState *s)
  */
 static void migration_completion(MigrationState *s)
 {
-    int ret = 0;
     Error *local_err = NULL;
 
     if (s->state == MIGRATION_STATUS_ACTIVE) {
-        ret = migration_completion_precopy(s, &local_err);
+        if (!migration_completion_precopy(s, &local_err)) {
+            goto fail;
+        }
     } else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         migration_completion_postcopy(s);
     } else {
-        ret = -1;
+        error_setg(&local_err, "Unexpected migration completion status %s",
-    }
+                   MigrationStatus_str(s->state));
-
-    if (ret < 0) {
         goto fail;
     }
 
@@ -2945,12 +2943,7 @@ static void migration_completion(MigrationState *s)
     return;
 
 fail:
-    if (local_err) {
+    if (local_err || qemu_file_get_error_obj(s->to_dst_file, &local_err)) {
-        migrate_error_propagate(s, local_err);
-    } else if (qemu_file_get_error_obj(s->to_dst_file, &local_err)) {
-        migrate_error_propagate(s, local_err);
-    } else if (ret) {
-        error_setg_errno(&local_err, -ret, "Error in migration completion");
         migrate_error_propagate(s, local_err);
     }
 
@@ -3863,7 +3856,7 @@ static void *bg_migration_thread(void *opaque)
         goto fail_with_bql;
     }
 
-    if (qemu_savevm_state_non_iterable(fb, &local_err)) {
+    if (!qemu_savevm_state_non_iterable(fb, &local_err)) {
         error_prepend(&local_err, "Failed to save non-iterable devices ");
         goto fail_with_bql;
     }

migration/savevm.c

@@ -1737,13 +1737,12 @@ void qemu_savevm_state_end_precopy(MigrationState *s, QEMUFile *f)
     qemu_savevm_state_vm_desc(s, f);
 }
 
-int qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp)
+bool qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp)
 {
     MigrationState *ms = migrate_get_current();
     int64_t start_ts_each, end_ts_each;
     JSONWriter *vmdesc = ms->vmdesc;
     SaveStateEntry *se;
-    int ret;
 
     /* Making sure cpu states are synchronized before saving non-iterable */
     cpu_synchronize_all_states();
@@ -1756,9 +1755,8 @@ int qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp)
 
         start_ts_each = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
 
-        ret = vmstate_save(f, se, vmdesc, errp);
+        if (vmstate_save(f, se, vmdesc, errp) < 0) {
-        if (ret) {
+            return false;
-            return ret;
         }
 
         end_ts_each = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
@@ -1768,10 +1766,10 @@ int qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp)
 
     trace_vmstate_downtime_checkpoint("src-non-iterable-saved");
 
-    return 0;
+    return true;
 }
 
-int qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp)
+bool qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp)
 {
     ERRP_GUARD();
     QEMUFile *f = s->to_dst_file;
@@ -1781,12 +1779,11 @@ int qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp)
     if (ret) {
         qemu_file_get_error_obj(f, errp);
         error_prepend(errp, "Failed to save iterable device state: ");
-        return ret;
+        return false;
     }
 
-    ret = qemu_savevm_state_non_iterable(f, errp);
+    if (!qemu_savevm_state_non_iterable(f, errp)) {
-    if (ret) {
+        return false;
-        return ret;
     }
 
     qemu_savevm_state_end_precopy(s, f);
@@ -1795,10 +1792,10 @@ int qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp)
     if (ret) {
         qemu_file_get_error_obj(f, errp);
         error_prepend(errp, "Failed to flush QEMUFile: ");
-        return ret;
+        return false;
     }
 
-    return 0;
+    return true;
 }
 
 static void qemu_savevm_query_pending(MigrationState *s,
@@ -1928,7 +1925,9 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
         goto cleanup;
     }
 
-    ret = qemu_savevm_state_complete_precopy(ms, errp);
+    if (!qemu_savevm_state_complete_precopy(ms, errp)) {
+        ret = -1;
+    }
 cleanup:
     qemu_savevm_state_cleanup();
 
@@ -1962,9 +1961,8 @@ int qemu_save_device_state(QEMUFile *f, Error **errp)
         return ret;
     }
 
-    ret = qemu_savevm_state_non_iterable(f, errp);
+    if (!qemu_savevm_state_non_iterable(f, errp)) {
-    if (ret) {
+        return -1;
-        return ret;
     }
 
     qemu_savevm_state_end(f);

migration/savevm.h

@@ -44,7 +44,7 @@ void qemu_savevm_state_header(QEMUFile *f);
 int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy);
 void qemu_savevm_state_cleanup(void);
 void qemu_savevm_state_complete_postcopy(QEMUFile *f);
-int qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp);
+bool qemu_savevm_state_complete_precopy(MigrationState *s, Error **errp);
 void qemu_savevm_query_pending_iter(MigrationState *s, MigPendingData *pending,
                                     bool exact);
 bool qemu_savevm_query_pending_final(MigrationState *s,
@@ -74,7 +74,7 @@ int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
                            Error **errp);
 int qemu_load_device_state(QEMUFile *f, Error **errp);
 int qemu_loadvm_approve_switchover(const char *approver);
-int qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp);
+bool qemu_savevm_state_non_iterable(QEMUFile *f, Error **errp);
 int qemu_savevm_state_non_iterable_early(QEMUFile *f,
                                          JSONWriter *vmdesc,
                                          Error **errp);