[Qemu-devel] [PATCH] savevm: Improve error message for unmigratable devices

[Kevin Wolf <kwolf@redhat.com>]

Trying to take an internal snapshot when an unmigratable device is in
use resuled in an 'Error -22 while writing VM' message. This patch
changes it to print the same error message as migration would print:
'State blocked by non-migratable device xyz'

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 savevm.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/savevm.c b/savevm.c
index 53515cb..1d00998 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1905,7 +1905,7 @@ void qemu_savevm_state_cancel(void)
     }
 }
 
-static int qemu_savevm_state(QEMUFile *f)
+static void qemu_savevm_state(QEMUFile *f, Error **errp)
 {
     int ret;
     MigrationParams params = {
@@ -1913,8 +1913,8 @@ static int qemu_savevm_state(QEMUFile *f)
         .shared = 0
     };
 
-    if (qemu_savevm_state_blocked(NULL)) {
-        return -EINVAL;
+    if (qemu_savevm_state_blocked(errp)) {
+        return;
     }
 
     qemu_mutex_unlock_iothread();
@@ -1934,8 +1934,8 @@ static int qemu_savevm_state(QEMUFile *f)
     }
     if (ret != 0) {
         qemu_savevm_state_cancel();
+        error_setg(errp, "Error %d while writing VM\n", ret);
     }
-    return ret;
 }
 
 static int qemu_save_device_state(QEMUFile *f)
@@ -2256,6 +2256,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
     qemu_timeval tv;
     struct tm tm;
     const char *name = qdict_get_try_str(qdict, "name");
+    Error *local_err = NULL;
 
     /* Verify if there is a device that doesn't support snapshots and is writable */
     bs = NULL;
@@ -2314,11 +2315,13 @@ void do_savevm(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "Could not open VM state file\n");
         goto the_end;
     }
-    ret = qemu_savevm_state(f);
+
+    qemu_savevm_state(f, &local_err);
     vm_state_size = qemu_ftell(f);
     qemu_fclose(f);
-    if (ret < 0) {
-        monitor_printf(mon, "Error %d while writing VM\n", ret);
+    if (error_is_set(&local_err)) {
+        qerror_report_err(local_err);
+        error_free(local_err);
         goto the_end;
     }
 
-- 
1.8.1.4