linux-kernel - Re: [PATCH] drivers: Conversions from kmalloc+memset to k(z|c)alloc.

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Date:	Wed, 19 Jul 2006 14:53:31 +0100
From:	Paulo Marques <pmarques@...popie.com>
To:	Panagiotis Issaris <takis@...umba.uhasselt.be>
CC:	linux-kernel@...r.kernel.org, len.brown@...el.com,
	chas@....nrl.navy.mil, miquel@...uba.ar, kkeil@...e.de,
	benh@...nel.crashing.org, video4linux-list@...hat.com,
	rmk+mmc@....linux.org.uk, Neela.Kolli@...enio.com,
	jgarzik@...ox.com, vandrove@...cvut.cz, adaplas@....net,
	thomas@...ischhofer.net, weissg@...nna.at, philb@....org,
	linux-pcmcia@...ts.infradead.org, jkmaline@...hut.fi,
	paulus@...ba.org
Subject: Re: [PATCH] drivers: Conversions from kmalloc+memset to k(z|c)alloc.

Panagiotis Issaris wrote:
> [...]
> --- a/drivers/char/consolemap.c
> +++ b/drivers/char/consolemap.c
> @@ -192,11 +192,9 @@ static void set_inverse_transl(struct vc
>  	q = p->inverse_translations[i];
>  
>  	if (!q) {
> -		q = p->inverse_translations[i] = (unsigned char *) 
> -			kmalloc(MAX_GLYPH, GFP_KERNEL);
> +		q = p->inverse_translations[i] = kzalloc(MAX_GLYPH, GFP_KERNEL);
>  		if (!q) return;
>  	}
> -	memset(q, 0, MAX_GLYPH);

This changes semantics here. Before, the data pointed by q was always 
cleared whether it was malloc'ed or not. Now it is only cleared if it is 
malloc'ed. I haven't checked the code to find out if this is ok, though.

> @@ -2704,8 +2702,7 @@ static void cardmap_set(struct cardmap *
>  	if (p == NULL || (nr >> p->shift) >= CARDMAP_WIDTH) {
>  		do {
>  			/* need a new top level */
> -			struct cardmap *np = kmalloc(sizeof(*np), GFP_KERNEL);
> -			memset(np, 0, sizeof(*np));
> +			struct cardmap *np = kzalloc(sizeof(*np), GFP_KERNEL);
>  			np->ptr[0] = p;
>  			if (p != NULL) {
>  				np->shift = p->shift + CARDMAP_ORDER;
> @@ -2719,8 +2716,7 @@ static void cardmap_set(struct cardmap *
>  	while (p->shift > 0) {
>  		i = (nr >> p->shift) & CARDMAP_MASK;
>  		if (p->ptr[i] == NULL) {
> -			struct cardmap *np = kmalloc(sizeof(*np), GFP_KERNEL);
> -			memset(np, 0, sizeof(*np));
> +			struct cardmap *np = kzalloc(sizeof(*np), GFP_KERNEL);
>  			np->shift = p->shift - CARDMAP_ORDER;
>  			np->parent = p;
>  			p->ptr[i] = np;

This is not your fault, but this code is using the return value from 
kmalloc (or kzalloc, now) without checking for NULL.

> diff --git a/drivers/scsi/megaraid.c b/drivers/scsi/megaraid.c
> index 76edbb6..71d4743 100644
> --- a/drivers/scsi/megaraid.c
> +++ b/drivers/scsi/megaraid.c
> @@ -4487,8 +4487,7 @@ mega_internal_command(adapter_t *adapter
>  	scmd = &adapter->int_scmd;
>  	memset(scmd, 0, sizeof(Scsi_Cmnd));
>  
> -	sdev = kmalloc(sizeof(struct scsi_device), GFP_KERNEL);
> -	memset(sdev, 0, sizeof(struct scsi_device));
> +	sdev = kzalloc(sizeof(struct scsi_device), GFP_KERNEL);
>  	scmd->device = sdev;
>  
>  	scmd->device->host = adapter->host;

Same here.

> --- a/drivers/video/offb.c
> +++ b/drivers/video/offb.c
> @@ -376,13 +376,12 @@ static void __init offb_init_fb(const ch
>  
>  	size = sizeof(struct fb_info) + sizeof(u32) * 17;
>  
> -	info = kmalloc(size, GFP_ATOMIC);
> +	info = kzalloc(size, GFP_ATOMIC);
>  	
>  	if (info == 0) {

Again, not your fault, but "info == 0"? If you're doing a new version of 
the patch, please change this to NULL or !info, so that we don't confuse 
human readers :)

-- 
Paulo Marques - www.grupopie.com

"I can picture in my mind a world without war, a world
without hate. And I can picture us attacking that world,
because they'd never expect it."
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