[PATCH RESEND] xenbus: check return value of xenbus_scanf()

[Jan Beulich]

Don't ignore errors here: Set backend state to unknown when
unsuccessful.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 drivers/xen/xenbus/xenbus_probe_frontend.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- 4.9-rc2/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ 4.9-rc2-xenbus-xenbus_scanf/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -335,7 +335,9 @@ static int backend_state;
 static void xenbus_reset_backend_state_changed(struct xenbus_watch *w,
 					const char **v, unsigned int l)
 {
-	xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &backend_state);
+	if (xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i",
+			 &backend_state) != 1)
+		backend_state = XenbusStateUnknown;
 	printk(KERN_DEBUG "XENBUS: backend %s %s\n",
 			v[XS_WATCH_PATH], xenbus_strstate(backend_state));
 	wake_up(&backend_state_wq);