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SubjectRe: Uninline kcalloc
On Tue, 14 Feb 2012 13:37:44 -0600 (CST)
Christoph Lameter <cl@linux.com> wrote:

> This patch still preserves kcalloc. But note that if kcalloc returns NULL
> then multiple conditions may have caused it. One is that the array is
> simply too large. The other may be that such an allocation is not possible
> due to fragmentation.
>
>
> Subject: Introduce calculate_array_size
>
> calculate_array_size calculates the size of an array while
> checking for errors. Returns 0 if the size is too large.
>
> Signed-off-by: Christoph Lameter <cl@linux.com>
>
>
> ---
> include/linux/slab.h | 15 +++++++++++++++
> mm/util.c | 9 ++++++---
> 2 files changed, 21 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/include/linux/slab.h
> ===================================================================
> --- linux-2.6.orig/include/linux/slab.h 2012-02-14 13:32:43.000000000 -0600
> +++ linux-2.6/include/linux/slab.h 2012-02-14 13:34:41.000000000 -0600
> @@ -242,6 +242,21 @@ size_t ksize(const void *);
> */
> void *kcalloc(size_t n, size_t size, gfp_t flags);
>
> +/*
> + * calculate_array_size - Calculate an array size given the size of a
> + * particular element with checking for overflow.
> + *
> + * Return 0 if there is an overflow.
> + */
> +static inline long calculate_array_size(size_t n, size_t size)
> +{
> + if (size != 0 && n > ULONG_MAX / size)
> +
> + return 0;
> +
> + return n * size;
> +}
> +
> #if !defined(CONFIG_NUMA) && !defined(CONFIG_SLOB)
> /**
> * kmalloc_node - allocate memory from a specific node
> Index: linux-2.6/mm/util.c
> ===================================================================
> --- linux-2.6.orig/mm/util.c 2012-02-14 13:32:54.000000000 -0600
> +++ linux-2.6/mm/util.c 2012-02-14 13:34:10.000000000 -0600
> @@ -83,9 +83,12 @@ EXPORT_SYMBOL(kmemdup);
> */
> 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);
> + size_t s = calculate_array_size(n, size);
> +
> + if (s)
> + return kzalloc(s, flags);
> +
> + return NULL;
> }
> EXPORT_SYMBOL(kcalloc);

The patch appears to be a no-op. Confused.



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