figo1802 at gmail
Jul 4, 2009, 8:11 PM
Post #3 of 3
(95 views)
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Re: [PATCH]mempool.c : clean up type-casting twice
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On Sun, 2009-07-05 at 05:01 +0200, Ingo Molnar wrote:
> * Figo.zhang <figo1802[at]gmail.com> wrote:
>
> > clean up type-casting twice
> >
> > Signed-off-by: Figo.zhang <figo1802[at]gmail.com>
> > ---
> > mm/mempool.c | 6 +++---
> > 1 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/mempool.c b/mm/mempool.c
> > index a46eb1b..0aec628 100644
> > --- a/mm/mempool.c
> > +++ b/mm/mempool.c
> > @@ -303,7 +303,7 @@ EXPORT_SYMBOL(mempool_free_slab);
> > */
> > void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
> > {
> > - size_t size = (size_t)(long)pool_data;
> > + size_t size = (size_t)pool_data;
> > return kmalloc(size, gfp_mask);
> > }
> > EXPORT_SYMBOL(mempool_kmalloc);
> > @@ -327,14 +327,14 @@ EXPORT_SYMBOL(mempool_kfree);
> > */
> > void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
> > {
> > - int order = (int)(long)pool_data;
> > + int order = (int)pool_data;
> > return alloc_pages(gfp_mask, order);
> > }
> > EXPORT_SYMBOL(mempool_alloc_pages);
> >
> > void mempool_free_pages(void *element, void *pool_data)
> > {
> > - int order = (int)(long)pool_data;
> > + int order = (int)pool_data;
> > __free_pages(element, order);
>
> What's the motivation?
>
> On 64-bit platforms, casting from a pointer (64-bit) straight to int
> (32-bit) can lose information and is thus a potential source of
> bugs, so certain compilers will warn about it with:
>
> warning: cast from pointer to integer of different size
>
> The double cast is a "I know what I'm doing" signal.
>
thanks.
void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
{
size_t size = (size_t)(long)pool_data;
return kmalloc(size, gfp_mask);
}
void *mempool_kzalloc(gfp_t gfp_mask, void *pool_data)
{
size_t size = (size_t) pool_data;
return kzalloc(size, gfp_mask);
}
at this point, is it no need for type-casting twice ? because size_t is
typedef "unsigned int" in x86_32, "unsigned long " in x86_64.
Best,
Figo.zhang
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