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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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