[PATCH v2] xen/manage: correct return value check on xenbus_scanf()

["Jan Beulich" <JBeulich@suse.com>]

A negative return value indicates an error; in fact the function at
present won't ever return zero.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: For consistency with other code don't consider zero an error
    (utilizing that xenbus_scanf() at present won't return zero).
    Adjust commit message accordingly.
---
 drivers/xen/manage.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 4.9-rc4/drivers/xen/manage.c
+++ 4.9-rc4-xen-manage-xenbus_scanf/drivers/xen/manage.c
@@ -277,7 +277,7 @@ static void sysrq_handler(struct xenbus_
 	err = xenbus_transaction_start(&xbt);
 	if (err)
 		return;
-	if (!xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key)) {
+	if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) {
 		pr_err("Unable to read sysrq code in control/sysrq\n");
 		xenbus_transaction_end(xbt, 1);
 		return;