migration: respect exit status with exec:

This patch makes sure that if the exec: process exits with a non-zero return
status, we treat the migration as failed.

This fixes https://bugs.launchpad.net/qemu/+bug/391879

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/migration.c b/migration.c
index 706fe55..fbf2339 100644
--- a/migration.c
+++ b/migration.c
@@ -252,13 +252,17 @@
     migrate_fd_cleanup(s);
 }
 
-void migrate_fd_cleanup(FdMigrationState *s)
+int migrate_fd_cleanup(FdMigrationState *s)
 {
+    int ret = 0;
+
     qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
 
     if (s->file) {
         DPRINTF("closing file\n");
-        qemu_fclose(s->file);
+        if (qemu_fclose(s->file) != 0) {
+            ret = -1;
+        }
         s->file = NULL;
     }
 
@@ -271,6 +275,8 @@
     }
 
     s->fd = -1;
+
+    return ret;
 }
 
 void migrate_fd_put_notify(void *opaque)
@@ -349,7 +355,12 @@
         } else {
             state = MIG_STATE_COMPLETED;
         }
-        migrate_fd_cleanup(s);
+        if (migrate_fd_cleanup(s) < 0) {
+            if (old_vm_running) {
+                vm_start();
+            }
+            state = MIG_STATE_ERROR;
+        }
         s->state = state;
     }
 }