xen: don't print error message in case of missing Xenstore entry

[ Upstream commit 4e93b6481c87ea5afde944a32b4908357ec58992 ]

When registering for the Xenstore watch of the node control/sysrq the
handler will be called at once. Don't issue an error message if the
Xenstore node isn't there, as it will be created only when an event
is being triggered.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index f905ba624b8d0dc6ca31851c65ade7b4be838766..77909a2c672388a2dd9c9d1181aa56d2ab48307b 100644 (file)
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -272,8 +272,16 @@ static void sysrq_handler(struct xenbus_watch *watch, const char **vec,
        err = xenbus_transaction_start(&xbt);
        if (err)
                return;
-       if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) {
-               pr_err("Unable to read sysrq code in control/sysrq\n");
+       err = xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key);
+       if (err < 0) {
+               /*
+                * The Xenstore watch fires directly after registering it and
+                * after a suspend/resume cycle. So ENOENT is no error but
+                * might happen in those cases.
+                */
+               if (err != -ENOENT)
+                       pr_err("Error %d reading sysrq code in control/sysrq\n",
+                              err);
                xenbus_transaction_end(xbt, 1);
                return;
        }