Re: [Qemu-devel] [PATCH V7 4/6] qcow2: cancel the modification on fail in qcow2_snapshot_create()

[Wenchao Xia]

于 2013/12/20 22:20, Stefan Hajnoczi 写道:

On Thu, Dec 05, 2013 at 08:02:50PM +0800, Wenchao Xia wrote:

+restore_refcount:
+    if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1)
+        < 0 && errp) {
+        /* Nothing can be done now, need image check later */
+        error_setg(&err, "%s\nqcow2: Error in restoring refcount in snapshot",
+                   error_get_pretty(*errp));
+        error_free(*errp);
+        *errp = NULL;
+        error_propagate(errp, err);
+    }

We get here if writing the new snapshot list failed.  If
qcow2_update_snapshot_refcount(..., -1) also fails I think we should
skip qcow2_free_clusters() below.  We don't know the exact state of the
disk image anymore - better to leak clusters than to have a dangling
reference.

  Make sense, dangling point should be avoid in any case, will fix,
Thanks for reviewing!

+dealloc_cluster:
+    qcow2_free_clusters(bs, sn->l1_table_offset,
+                        sn->l1_size * sizeof(uint64_t),
+                        QCOW2_DISCARD_ALWAYS);
+
  fail:
      g_free(sn->id_str);
      g_free(sn->name);
--
1.7.1