[Qemu-devel] [PATCH RFC] migration: Convert 'status' of MigrationInfo to use an enum type

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

The original 'status' is an open-coded 'str' type, convert it to use an
enum type.
This conversion is backwards compatible, better documented and
more convenient for future extensibility.

In addition, Fix a typo for qapi-schema.json: comppleted -> completed

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
---
Hi,

This conversion from open-coded 'str' type to enum type for 'status'
is suggested by Eric, thanks for his comment.

Actually, I will add a MIG_STATE_COLO state for COLO, and i also
saw David added MIG_STATE_POSTCOPY_ACTIVE for postcopy, after
this conversion, it will be more convenient for us to add a new state.

One more thing, i have to replace MIG_STATE_ERROR with MIG_STATE_FAILED,
and it begin from 0, not its original -1. I think it has no side effect.

Please review.

Thanks
---
 hmp.c                 |  7 ++++---
 migration/migration.c | 37 +++++++++++++++----------------------
 qapi-schema.json      | 34 +++++++++++++++++++++++++++++-----
 3 files changed, 48 insertions(+), 30 deletions(-)

diff --git a/hmp.c b/hmp.c
index 3825b29..8cbd135 100644
--- a/hmp.c
+++ b/hmp.c
@@ -158,7 +158,8 @@ void hmp_info_migrate(Monitor *mon, const QDict *qdict)
     }
 
     if (info->has_status) {
-        monitor_printf(mon, "Migration status: %s\n", info->status);
+        monitor_printf(mon, "Migration status: %s\n",
+                       MigState_lookup[info->status]);
         monitor_printf(mon, "total time: %" PRIu64 " milliseconds\n",
                        info->total_time);
         if (info->has_expected_downtime) {
@@ -1312,8 +1313,8 @@ static void hmp_migrate_status_cb(void *opaque)
     MigrationInfo *info;
 
     info = qmp_query_migrate(NULL);
-    if (!info->has_status || strcmp(info->status, "active") == 0 ||
-        strcmp(info->status, "setup") == 0) {
+    if (!info->has_status || info->status == MIG_STATE_ACTIVE ||
+        info->status == MIG_STATE_SETUP) {
         if (info->has_disk) {
             int progress;
 
diff --git a/migration/migration.c b/migration/migration.c
index b3adbc6..8b8fbbf 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -26,16 +26,6 @@
 #include "qmp-commands.h"
 #include "trace.h"
 
-enum {
-    MIG_STATE_ERROR = -1,
-    MIG_STATE_NONE,
-    MIG_STATE_SETUP,
-    MIG_STATE_CANCELLING,
-    MIG_STATE_CANCELLED,
-    MIG_STATE_ACTIVE,
-    MIG_STATE_COMPLETED,
-};
-
 #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
 
 /* Amount of time to allocate to each "chunk" of bandwidth-throttled
@@ -189,13 +179,16 @@ MigrationInfo *qmp_query_migrate(Error **errp)
         break;
     case MIG_STATE_SETUP:
         info->has_status = true;
-        info->status = g_strdup("setup");
+        info->status = MIG_STATE_SETUP;
         info->has_total_time = false;
         break;
     case MIG_STATE_ACTIVE:
     case MIG_STATE_CANCELLING:
         info->has_status = true;
-        info->status = g_strdup("active");
+        /* Note: when the real state of migration is 'cancelling',
+         we still return 'active' status to user, it makes no difference
+         for user. */
+        info->status = MIG_STATE_ACTIVE;
         info->has_total_time = true;
         info->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME)
             - s->total_time;
@@ -231,7 +224,7 @@ MigrationInfo *qmp_query_migrate(Error **errp)
         get_xbzrle_cache_stats(info);
 
         info->has_status = true;
-        info->status = g_strdup("completed");
+        info->status = MIG_STATE_COMPLETED;
         info->has_total_time = true;
         info->total_time = s->total_time;
         info->has_downtime = true;
@@ -251,13 +244,13 @@ MigrationInfo *qmp_query_migrate(Error **errp)
         info->ram->mbps = s->mbps;
         info->ram->dirty_sync_count = s->dirty_sync_count;
         break;
-    case MIG_STATE_ERROR:
+    case MIG_STATE_FAILED:
         info->has_status = true;
-        info->status = g_strdup("failed");
+        info->status = MIG_STATE_FAILED;
         break;
     case MIG_STATE_CANCELLED:
         info->has_status = true;
-        info->status = g_strdup("cancelled");
+        info->status = MIG_STATE_CANCELLED;
         break;
     }
 
@@ -322,8 +315,8 @@ void migrate_fd_error(MigrationState *s)
 {
     trace_migrate_fd_error();
     assert(s->file == NULL);
-    s->state = MIG_STATE_ERROR;
-    trace_migrate_set_state(MIG_STATE_ERROR);
+    s->state = MIG_STATE_FAILED;
+    trace_migrate_set_state(MIG_STATE_FAILED);
     notifier_list_notify(&migration_state_notifiers, s);
 }
 
@@ -376,7 +369,7 @@ bool migration_has_finished(MigrationState *s)
 bool migration_has_failed(MigrationState *s)
 {
     return (s->state == MIG_STATE_CANCELLED ||
-            s->state == MIG_STATE_ERROR);
+            s->state == MIG_STATE_FAILED);
 }
 
 static MigrationState *migrate_init(const MigrationParams *params)
@@ -465,7 +458,7 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
 #endif
     } else {
         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "uri", "a valid migration protocol");
-        s->state = MIG_STATE_ERROR;
+        s->state = MIG_STATE_FAILED;
         return;
     }
 
@@ -627,7 +620,7 @@ static void *migration_thread(void *opaque)
                 qemu_mutex_unlock_iothread();
 
                 if (ret < 0) {
-                    migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_ERROR);
+                    migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_FAILED);
                     break;
                 }
 
@@ -639,7 +632,7 @@ static void *migration_thread(void *opaque)
         }
 
         if (qemu_file_get_error(s->file)) {
-            migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_ERROR);
+            migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_FAILED);
             break;
         }
         current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
diff --git a/qapi-schema.json b/qapi-schema.json
index e16f8eb..89b14a9 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -411,18 +411,42 @@
            'overflow': 'int' } }
 
 ##
+# @MigState:
+#
+# An enumeration of migration status.
+#
+# @failed: some error occurred during migration process. (since 0.14.0)
+#
+# @none: no migration has happened ever.
+#
+# @setup: migration process has been initiated. (since 0.14.0)
+#
+# @cancelling: in the process of cancelling migration. (since 2.0)
+#
+# @cancelled: cancelling migration is finished. (since 0.14.0)
+#
+# @active: in the process of doing migration. (since 0.14.0)
+#
+# @completed: migration is finished. (since 0.14.0)
+#
+# Since: 2.3
+##
+{ 'enum': 'MigState',
+  'data': [ 'failed', 'none', 'setup', 'cancelling', 'cancelled',
+            'active', 'completed' ] }
+
+##
 # @MigrationInfo
 #
 # Information about current migration process.
 #
-# @status: #optional string describing the current migration status.
-#          As of 0.14.0 this can be 'setup', 'active', 'completed', 'failed' or
-#          'cancelled'. If this field is not returned, no migration process
+# @status: #optional @MigState describing the current migration status.
+#          If this field is not returned, no migration process
 #          has been initiated
 #
 # @ram: #optional @MigrationStats containing detailed migration
 #       status, only returned if status is 'active' or
-#       'completed'. 'comppleted' (since 1.2)
+#       'completed'. 'completed' (since 1.2)
 #
 # @disk: #optional @MigrationStats containing detailed disk migration
 #        status, only returned if status is 'active' and it is a block
@@ -453,7 +477,7 @@
 # Since: 0.14.0
 ##
 { 'type': 'MigrationInfo',
-  'data': {'*status': 'str', '*ram': 'MigrationStats',
+  'data': {'*status': 'MigState', '*ram': 'MigrationStats',
            '*disk': 'MigrationStats',
            '*xbzrle-cache': 'XBZRLECacheStats',
            '*total-time': 'int',
-- 
1.7.12.4