linux-kernel - Re: [PATCH 1/7] iscsi-target: Use a variable initialisation in iscsi_set_default

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Message-ID: <20151214084114.GB31151@c203.arch.suse.de>
Date:	Mon, 14 Dec 2015 09:41:14 +0100
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	SF Markus Elfring <elfring@...rs.sourceforge.net>,
	linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH 1/7] iscsi-target: Use a variable initialisation in
 iscsi_set_default_param() directly

On Sat, Dec 12, 2015 at 10:49:40PM +0300, Dan Carpenter wrote:
> On Sat, Dec 12, 2015 at 03:34:50PM +0100, SF Markus Elfring wrote:
> > From: Markus Elfring <elfring@...rs.sourceforge.net>
> > Date: Sat, 12 Dec 2015 11:36:02 +0100
> > 
> > Omit the unnecessary setting to a null pointer for the variable "param"
> > at the beginning of the function "iscsi_set_default_param"
> > because it can be directly initialized with the return value
> > from the function "kzalloc".
> > 
> > Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> > ---
> >  drivers/target/iscsi/iscsi_target_parameters.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/target/iscsi/iscsi_target_parameters.c b/drivers/target/iscsi/iscsi_target_parameters.c
> > index 3a1f9a7..0a8bd3f 100644
> > --- a/drivers/target/iscsi/iscsi_target_parameters.c
> > +++ b/drivers/target/iscsi/iscsi_target_parameters.c
> > @@ -127,9 +127,8 @@ static struct iscsi_param *iscsi_set_default_param(struct iscsi_param_list *para
> >  		char *name, char *value, u8 phase, u8 scope, u8 sender,
> >  		u16 type_range, u8 use)
> >  {
> > -	struct iscsi_param *param = NULL;
> > +	struct iscsi_param *param = kzalloc(sizeof(*param), GFP_KERNEL);
> >  
> > -	param = kzalloc(sizeof(struct iscsi_param), GFP_KERNEL);
> >  	if (!param) {
> >  		pr_err("Unable to allocate memory for parameter.\n");
> >  		goto out;
> 
> It's better to just get rid of the initialization but leave the
> kzalloc() as-is for two reasons.
> 
> 1)  Initializer code normally contains more bugs per line than other
>     code.  I am thinking about dereferencing pointers before checking
>     for NULL or not checking the allocation for failure.
> 
> 2)  It puts a blank line between the allocation and the check for
>     failure.  It's like a new paragraph.  The allocation and the check
>     should be next to each other.

I agree with Dan here. Please don't do it.

@@ -127,9 +127,8 @@ static struct iscsi_param *iscsi_set_default_param(struct iscsi_param_list *para
 		char *name, char *value, u8 phase, u8 scope, u8 sender,
 		u16 type_range, u8 use)
 {
-	struct iscsi_param *param = NULL;
+	struct iscsi_param *param;
 
	param = kzalloc(sizeof(struct iscsi_param), GFP_KERNEL);
 	if (!param) {
 		pr_err("Unable to allocate memory for parameter.\n");


This way it would be _far_ more readable. IMHO one should have a 1 action per
line of code style and only assign values in at declaration time if really 
necessary.

But what is the benefit from this? Is it fixing a (hypothetical) bug? I somehow
fail to see it.

Thanks,
	Johannes

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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