[RFC PATCH 2/4] migration: Fix state transition in postcopy_start() error handling

[Juraj Marcin <jmarcin@redhat.com>]

From: Juraj Marcin <jmarcin@redhat.com>

Depending on where an error during postcopy_start() happens, the state
can be either "active", "device" or "cancelling", but never
"postcopy-active". Migration state is transitioned to "postcopy-active"
only just before a successful return from the function.

Accept any state except "cancelling" when transitioning to "failed"
state.

Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
---
 migration/migration.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 10c216d25d..e5ce2940d5 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2872,8 +2872,9 @@ static int postcopy_start(MigrationState *ms, Error **errp)
 fail_closefb:
     qemu_fclose(fb);
 fail:
-    migrate_set_state(&ms->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
-                          MIGRATION_STATUS_FAILED);
+    if ( ms->state != MIGRATION_STATUS_CANCELLING) {
+        migrate_set_state(&ms->state, ms->state, MIGRATION_STATUS_FAILED);
+    }
     migration_block_activate(NULL);
     migration_call_notifiers(ms, MIG_EVENT_PRECOPY_FAILED, NULL);
     bql_unlock();
-- 
2.50.1