linux-kernel - Re: [PATCH] drivers: Use kzalloc instead of 'kmalloc+memset', where possible.

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Date:	Tue, 24 May 2011 10:09:31 -0700
From:	Joe Perches <joe@...ches.com>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] drivers: Use kzalloc instead of 'kmalloc+memset',
 where possible.

On Tue, 2011-05-24 at 22:59 +0600, Rakib Mullick wrote:
> On 5/23/11, Joe Perches <joe@...ches.com> wrote:
> > On Mon, 2011-05-23 at 23:40 +0600, Rakib Mullick wrote:
> >> Following patch removes the uses of 'kmalloc+memset' from various
> >> drivers subsystems, which is replaced by kzalloc. kzalloc take care of
> >> setting allocated memory with null, so it helps to get rid from using
> >> memset.
> >> diff --git a/drivers/gpu/drm/drm_scatter.c b/drivers/gpu/drm/drm_scatter.c
> > []
> >> -	entry->pagelist = kmalloc(pages * sizeof(*entry->pagelist), GFP_KERNEL);
> >> +	entry->pagelist = kzalloc(pages * sizeof(*entry->pagelist), GFP_KERNEL);
> > Perhaps it's better to use:
> > 	entry->pagelist =  kcalloc(pages, sizeof(*entry->pagelist), GFP_KERNEL);
> >> -	entry->busaddr = kmalloc(pages * sizeof(*entry->busaddr), GFP_KERNEL);
> >> +	entry->busaddr = kzalloc(pages * sizeof(*entry->busaddr), GFP_KERNEL);
> > here too.
> Is there any significant benefit of using kcalloc here?

Overflow and tradition.

static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
{
	if (size != 0 && n > ULONG_MAX / size)
		return NULL;
	return __kmalloc(n * size, flags | __GFP_ZERO);
}


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