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slab: fix wrongly used macro

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commit 'slab: restrict the number of objects in a slab' uses
__builtin_constant_p() on #if macro. It is wrong usage of builtin
function, but it is compiled on x86 without any problem, so I can't
find it before 0 day build system find it.

This commit fixes the situation by using KMALLOC_MIN_SIZE, instead of
KMALLOC_SHIFT_LOW. KMALLOC_SHIFT_LOW is parsed to ilog2() on some
architecture and this ilog2() uses __builtin_constant_p() and results in
the problem. This problem would disappear by using KMALLOC_MIN_SIZE,
since it is just constant.

Tested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Joonsoo Kim 2014-03-12 17:06:19 +09:00 • committed by Pekka Enberg
parent 80c3a9981a
commit 24f870d8f0
1 changed files with 11 additions and 11 deletions
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22
include/linux/slab.h
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@ -201,17 +201,6 @@ struct kmem_cache {
#ifndef KMALLOC_SHIFT_LOW #ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 5 #define KMALLOC_SHIFT_LOW 5
#endif #endif
/*
* This restriction comes from byte sized index implementation.
* Page size is normally 2^12 bytes and, in this case, if we want to use
* byte sized index which can represent 2^8 entries, the size of the object
* should be equal or greater to 2^12 / 2^8 = 2^4 = 16.
* If minimum size of kmalloc is less than 16, we use it as minimum object
* size and give up to use byte sized index.
*/
#define SLAB_OBJ_MIN_SIZE (KMALLOC_SHIFT_LOW < 4 ? \
(1 << KMALLOC_SHIFT_LOW) : 16)
#endif #endif
#ifdef CONFIG_SLUB #ifdef CONFIG_SLUB
@ -253,6 +242,17 @@ struct kmem_cache {
#define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW) #define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW)
#endif #endif
/*
* This restriction comes from byte sized index implementation.
* Page size is normally 2^12 bytes and, in this case, if we want to use
* byte sized index which can represent 2^8 entries, the size of the object
* should be equal or greater to 2^12 / 2^8 = 2^4 = 16.
* If minimum size of kmalloc is less than 16, we use it as minimum object
* size and give up to use byte sized index.
*/
#define SLAB_OBJ_MIN_SIZE (KMALLOC_MIN_SIZE < 16 ? \
(KMALLOC_MIN_SIZE) : 16)
#ifndef CONFIG_SLOB #ifndef CONFIG_SLOB
extern struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1]; extern struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];
#ifdef CONFIG_ZONE_DMA #ifdef CONFIG_ZONE_DMA