linux-kernel - [PATCH v2] xen/manage: correct return value check on xenbus

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Message-Id: <58219077020000780011CF59@prv-mh.provo.novell.com>
Date:   Tue, 08 Nov 2016 00:44:39 -0700
From:   "Jan Beulich" <JBeulich@...e.com>
To:     <david.vrabel@...rix.com>, <boris.ostrovsky@...cle.com>,
        "Juergen Gross" <JGross@...e.com>
Cc:     <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] xen/manage: correct return value check on
 xenbus_scanf()

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

Signed-off-by: Jan Beulich <jbeulich@...e.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;