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>

migration-exec.c

@@ -43,13 +43,21 @@ static int file_write(FdMigrationState *s, const void * buf, size_t size)
 
 static int exec_close(FdMigrationState *s)
 {
+    int ret = 0;
     DPRINTF("exec_close\n");
     if (s->opaque) {
-        qemu_fclose(s->opaque);
+        ret = qemu_fclose(s->opaque);
         s->opaque = NULL;
         s->fd = -1;
+        if (ret != -1 &&
+            WIFEXITED(ret)
+            && WEXITSTATUS(ret) == 0) {
+            ret = 0;
+        } else {
+            ret = -1;
+        }
     }
-    return 0;
+    return ret;
 }
 
 MigrationState *exec_start_outgoing_migration(Monitor *mon,

migration.c

@@ -252,13 +252,17 @@ void migrate_fd_error(FdMigrationState *s)
     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 @@ void migrate_fd_cleanup(FdMigrationState *s)
     }
 
     s->fd = -1;
+
+    return ret;
 }
 
 void migrate_fd_put_notify(void *opaque)
@@ -349,7 +355,12 @@ void migrate_fd_put_ready(void *opaque)
         } 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;
     }
 }

migration.h

@@ -107,7 +107,7 @@ void migrate_fd_monitor_suspend(FdMigrationState *s, Monitor *mon);
 
 void migrate_fd_error(FdMigrationState *s);
 
-void migrate_fd_cleanup(FdMigrationState *s);
+int migrate_fd_cleanup(FdMigrationState *s);
 
 void migrate_fd_put_notify(void *opaque);
 

savevm.c

@@ -235,9 +235,10 @@ static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
 static int stdio_pclose(void *opaque)
 {
     QEMUFileStdio *s = opaque;
-    pclose(s->stdio_file);
+    int ret;
+    ret = pclose(s->stdio_file);
     qemu_free(s);
-    return 0;
+    return ret;
 }
 
 static int stdio_fclose(void *opaque)