xen: add error handling for xenbus_printf

When xenbus_printf fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling xenbus_printf.

Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 8835065029d3..c93d8ef8df34 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -289,8 +289,15 @@ static void sysrq_handler(struct xenbus_watch *watch, const char *path,
                 return;
         }
 
-        if (sysrq_key != '\0')
-                xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+        if (sysrq_key != '\0') {
+                err = xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+                if (err) {
+                        pr_err("%s: Error %d writing sysrq in control/sysrq\n",
+                               __func__, err);
+                        xenbus_transaction_end(xbt, 1);
+                        return;
+                }
+        }
 
         err = xenbus_transaction_end(xbt, 0);
         if (err == -EAGAIN)
@@ -342,7 +349,12 @@ static int setup_shutdown_watcher(void)
                         continue;
                 snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
                          shutdown_handlers[idx].command);
-                xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+                err = xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+                if (err) {
+                        pr_err("%s: Error %d writing %s\n", __func__,
+                                err, node);
+                        return err;
+                }
         }
 
         return 0;