[PATCH] migration: Truncate state file in xen-save-devices-state

[Dov Murik <dovmurik@linux.vnet.ibm.com>]

When running the xen-save-devices-state QMP command, if the filename
already exists it will be truncated before dumping the devices' state
into it.

Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
---

Note that I found the above issue while trying to debug
xen-load-devices-state which simply fails (prints "Configuration section
missing" to stderr) directly after xen-save-devices-state (in the same
VM).  I wonder if I should file a bug report as-is or investigate some
more.  Advice welcome.

-Dov

---
 migration/savevm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 304d98ff78..e1b26672cc 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2803,7 +2803,8 @@ void qmp_xen_save_devices_state(const char *filename, bool has_live, bool live,
     vm_stop(RUN_STATE_SAVE_VM);
     global_state_store_running();
 
-    ioc = qio_channel_file_new_path(filename, O_WRONLY | O_CREAT, 0660, errp);
+    ioc = qio_channel_file_new_path(filename, O_WRONLY | O_CREAT | O_TRUNC,
+                                    0660, errp);
     if (!ioc) {
         goto the_end;
     }
-- 
2.20.1