39d61db0ed
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>
57 lines
1.4 KiB
C
57 lines
1.4 KiB
C
#ifndef _ASM_GENERIC_PAGE_H
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#define _ASM_GENERIC_PAGE_H
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#ifdef __KERNEL__
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#ifndef __ASSEMBLY__
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#include <linux/log2.h>
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/*
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* non-const pure 2^n version of get_order
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* - the arch may override these in asm/bitops.h if they can be implemented
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* more efficiently than using the arch log2 routines
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* - we use the non-const log2() instead if the arch has defined one suitable
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*/
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#ifndef ARCH_HAS_GET_ORDER
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static inline __attribute__((const))
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int __get_order(unsigned long size, int page_shift)
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{
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#if BITS_PER_LONG == 32 && defined(ARCH_HAS_ILOG2_U32)
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int order = __ilog2_u32(size) - page_shift;
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return order >= 0 ? order : 0;
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#elif BITS_PER_LONG == 64 && defined(ARCH_HAS_ILOG2_U64)
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int order = __ilog2_u64(size) - page_shift;
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return order >= 0 ? order : 0;
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#else
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int order;
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size = (size - 1) >> (page_shift - 1);
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order = -1;
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do {
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size >>= 1;
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order++;
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} while (size);
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return order;
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#endif
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}
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#endif
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/**
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* get_order - calculate log2(pages) to hold a block of the specified size
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* @n - size
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*
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* calculate allocation order based on the current page size
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* - this can be used to initialise global variables from constant data
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*/
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#define get_order(n) \
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( \
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__builtin_constant_p(n) ? \
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((n < (1UL << PAGE_SHIFT)) ? 0 : ilog2(n) - PAGE_SHIFT) : \
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__get_order(n, PAGE_SHIFT) \
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)
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#endif /* __ASSEMBLY__ */
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#endif /* __KERNEL__ */
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#endif /* _ASM_GENERIC_PAGE_H */
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