[PATCH 3.18 26/27] xen: dont print error message in case of missing Xenstore entry

Greg Kroah-Hartman
2017-11-06T11:28:59Z

From: Juergen Gross <jgross@suse.com>

[ 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>
---
drivers/xen/manage.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -272,8 +272,16 @@ static void sysrq_handler(struct xenbus_
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;
}