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

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Date:   Tue, 8 Nov 2016 08:51:11 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>,
        David Vrabel <david.vrabel@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     xen-devel <xen-devel@...ts.xenproject.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] xen/manage: correct return value check on
 xenbus_scanf()

On 08/11/16 08:44, Jan Beulich wrote:
> 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>

Reviewed-by: Juergen Gross <jgross@...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;
> 
>