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Commit 24f870d8 authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Pekka Enberg
Browse files

slab: fix wrongly used macro 



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: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent 80c3a998

include/linux/slab.h

+11 −11
Original line number Diff line number Diff line
@@ -201,17 +201,6 @@ struct kmem_cache { 
#ifndef KMALLOC_SHIFT_LOW

#define KMALLOC_SHIFT_LOW	5

#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



#ifdef CONFIG_SLUB
@@ -253,6 +242,17 @@ struct kmem_cache { 
#define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW)

#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

extern struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];

#ifdef CONFIG_ZONE_DMA