On Wed, 17 Apr 2013, Steven Rostedt wrote:
> The slab.c code has a size check macro that checks the size of the
> following structs:
>
> struct arraycache_init
> struct kmem_list3
>
> The index_of() function that takes the sizeof() of the above two structs
> and does an unnecessary __builtin_constant_p() on that. As sizeof() will
> always end up being a constant making this always be true. The code is
> not incorrect, but it just adds added complexity, and confuses users and
> wastes the time of reviewers of the code, who spends time trying to
> figure out why the builtin_constant_p() was used.
>
> This patch is just a clean up that makes the index_of() code a little
> bit less complex.
>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Adding Pekka to the cc.
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 856e4a1..6047900 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -325,9 +325,7 @@ static void cache_reap(struct work_struct *unused);
> static __always_inline int index_of(const size_t size)
> {
> extern void __bad_size(void);
> -
> - if (__builtin_constant_p(size)) {
> - int i = 0;
> + int i = 0;
>
> #define CACHE(x) \
> if (size <=x) \
> @@ -336,9 +334,7 @@ static __always_inline int index_of(const size_t size)
> i++;
> #include <linux/kmalloc_sizes.h>
> #undef CACHE
> - __bad_size();
> - } else
> - __bad_size();
> + __bad_size();
> return 0;
> }
>
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