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| author | David Howells <dhowells@redhat.com> | 2006-12-08 02:37:52 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.osdl.org> | 2006-12-08 08:28:51 -0800 |
| commit | 39d61db0edb34d60b83c5e0d62d0e906578cc707 (patch) | |
| tree | 6bbf32fe84eaa8bd8e194aab278274039d2d6440 /include/asm-generic | |
| parent | 312a0c170945b49f319960afd2e492c05f9dd551 (diff) | |
| download | linux-39d61db0edb34d60b83c5e0d62d0e906578cc707.tar.bz2 | |
[PATCH] LOG2: Alter get_order() so that it can make use of ilog2() on a constant
Alter get_order() so that it can make use of ilog2() on a constant to produce
a constant value, retaining the ability for an arch to override it in the
non-const case.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/page.h | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h index a96b5d986b6e..b55052ce2330 100644 --- a/include/asm-generic/page.h +++ b/include/asm-generic/page.h @@ -4,21 +4,51 @@ #ifdef __KERNEL__ #ifndef __ASSEMBLY__ -#include <linux/compiler.h> +#include <linux/log2.h> -/* Pure 2^n version of get_order */ -static __inline__ __attribute_const__ int get_order(unsigned long size) +/* + * non-const pure 2^n version of get_order + * - the arch may override these in asm/bitops.h if they can be implemented + * more efficiently than using the arch log2 routines + * - we use the non-const log2() instead if the arch has defined one suitable + */ +#ifndef ARCH_HAS_GET_ORDER +static inline __attribute__((const)) +int __get_order(unsigned long size, int page_shift) { +#if BITS_PER_LONG == 32 && defined(ARCH_HAS_ILOG2_U32) + int order = __ilog2_u32(size) - page_shift; + return order >= 0 ? order : 0; +#elif BITS_PER_LONG == 64 && defined(ARCH_HAS_ILOG2_U64) + int order = __ilog2_u64(size) - page_shift; + return order >= 0 ? order : 0; +#else int order; - size = (size - 1) >> (PAGE_SHIFT - 1); + size = (size - 1) >> (page_shift - 1); order = -1; do { size >>= 1; order++; } while (size); return order; +#endif } +#endif + +/** + * get_order - calculate log2(pages) to hold a block of the specified size + * @n - size + * + * calculate allocation order based on the current page size + * - this can be used to initialise global variables from constant data + */ +#define get_order(n) \ +( \ + __builtin_constant_p(n) ? \ + ((n < (1UL << PAGE_SHIFT)) ? 0 : ilog2(n) - PAGE_SHIFT) : \ + __get_order(n, PAGE_SHIFT) \ + ) #endif /* __ASSEMBLY__ */ #endif /* __KERNEL__ */ |