According to writing-monitor-commands.rst, best practice is to
use the 'hmp_handle_error' function, which ensures that the
message gets an 'Error: ' prefix.

Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
---
 block/monitor/block-hmp-cmds.c | 43 +++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index 282d1c386e..2f79a7360d 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -62,7 +62,7 @@ static void hmp_drive_add_node(Monitor *mon, const char *optstr)
 {
     QemuOpts *opts;
     QDict *qdict;
-    Error *local_err = NULL;
+    Error *err = NULL;
 
     opts = qemu_opts_parse_noisily(&qemu_drive_opts, optstr, false);
     if (!opts) {
@@ -73,19 +73,19 @@ static void hmp_drive_add_node(Monitor *mon, const char *optstr)
 
     if (!qdict_get_try_str(qdict, "node-name")) {
         qobject_unref(qdict);
-        error_report("'node-name' needs to be specified");
+        error_setg(&err, "'node-name' needs to be specified");
         goto out;
     }
 
-    BlockDriverState *bs = bds_tree_init(qdict, &local_err);
+    BlockDriverState *bs = bds_tree_init(qdict, &err);
     if (!bs) {
-        error_report_err(local_err);
         goto out;
     }
 
     bdrv_set_monitor_owned(bs);
 out:
     qemu_opts_del(opts);
+    hmp_handle_error(mon, err);
 }
 
 void hmp_drive_add(Monitor *mon, const QDict *qdict)
@@ -109,7 +109,6 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict)
     mc = MACHINE_GET_CLASS(current_machine);
     dinfo = drive_new(opts, mc->block_default_type, &err);
     if (err) {
-        error_report_err(err);
         qemu_opts_del(opts);
         goto err;
     }
@@ -123,7 +122,7 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "OK\n");
         break;
     default:
-        monitor_printf(mon, "Can't hot-add drive to type %d\n", dinfo->type);
+        error_setg(&err, "Can't hot-add drive to type %d", dinfo->type);
         goto err;
     }
     return;
@@ -134,6 +133,7 @@ err:
         monitor_remove_blk(blk);
         blk_unref(blk);
     }
+    hmp_handle_error(mon, err);
 }
 
 void hmp_drive_del(Monitor *mon, const QDict *qdict)
@@ -141,36 +141,32 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
     const char *id = qdict_get_str(qdict, "id");
     BlockBackend *blk;
     BlockDriverState *bs;
-    Error *local_err = NULL;
+    Error *err = NULL;
 
     GLOBAL_STATE_CODE();
     bdrv_graph_rdlock_main_loop();
 
     bs = bdrv_find_node(id);
     if (bs) {
-        qmp_blockdev_del(id, &local_err);
-        if (local_err) {
-            error_report_err(local_err);
-        }
+        qmp_blockdev_del(id, &err);
         goto unlock;
     }
 
     blk = blk_by_name(id);
     if (!blk) {
-        error_report("Device '%s' not found", id);
+        error_setg(&err, "Device '%s' not found", id);
         goto unlock;
     }
 
     if (!blk_legacy_dinfo(blk)) {
-        error_report("Deleting device added with blockdev-add"
+        error_setg(&err, "Deleting device added with blockdev-add"
                      " is not supported");
         goto unlock;
     }
 
     bs = blk_bs(blk);
     if (bs) {
-        if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, &local_err)) {
-            error_report_err(local_err);
+        if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, &err)) {
             goto unlock;
         }
 
@@ -196,6 +192,7 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
 
 unlock:
     bdrv_graph_rdunlock_main_loop();
+    hmp_handle_error(mon, err);
 }
 
 void hmp_commit(Monitor *mon, const QDict *qdict)
@@ -203,6 +200,7 @@ void hmp_commit(Monitor *mon, const QDict *qdict)
     const char *device = qdict_get_str(qdict, "device");
     BlockBackend *blk;
     int ret;
+    Error *err = NULL;
 
     GLOBAL_STATE_CODE();
     GRAPH_RDLOCK_GUARD_MAINLOOP();
@@ -214,22 +212,25 @@ void hmp_commit(Monitor *mon, const QDict *qdict)
 
         blk = blk_by_name(device);
         if (!blk) {
-            error_report("Device '%s' not found", device);
-            return;
+            error_setg(&err, "Device '%s' not found", device);
+            goto end;
         }
 
         bs = bdrv_skip_implicit_filters(blk_bs(blk));
 
         if (!blk_is_available(blk)) {
-            error_report("Device '%s' has no medium", device);
-            return;
+            error_setg(&err, "Device '%s' has no medium", device);
+            goto end;
         }
 
         ret = bdrv_commit(bs);
     }
     if (ret < 0) {
-        error_report("'commit' error for '%s': %s", device, strerror(-ret));
+        error_setg(&err, "'commit' error for '%s': %s", device, strerror(-ret));
     }
+
+end:
+    hmp_handle_error(mon, err);
 }
 
 void hmp_drive_mirror(Monitor *mon, const QDict *qdict)
@@ -890,7 +891,7 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
 
     bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, &err);
     if (!bs) {
-        error_report_err(err);
+        hmp_handle_error(mon, err);
         return;
     }
 
-- 
2.39.5