e0891a9816
Adjust the comment on get_order() to note that the result of passing a size of 0 results in an undefined value. Signed-off-by: David Howells <dhowells@redhat.com> Link: http://lkml.kernel.org/r/20120220223917.16199.9416.stgit@warthog.procyon.org.uk Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
45 lines
1.1 KiB
C
45 lines
1.1 KiB
C
#ifndef __ASM_GENERIC_GETORDER_H
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#define __ASM_GENERIC_GETORDER_H
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#ifndef __ASSEMBLY__
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#include <linux/compiler.h>
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/**
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* get_order - Determine the allocation order of a memory size
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* @size: The size for which to get the order
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*
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* Determine the allocation order of a particular sized block of memory. This
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* is on a logarithmic scale, where:
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*
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* 0 -> 2^0 * PAGE_SIZE and below
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* 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
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* 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
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* 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
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* 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
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* ...
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*
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* The order returned is used to find the smallest allocation granule required
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* to hold an object of the specified size.
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*
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* The result is undefined if the size is 0.
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*
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* This function may be used to initialise variables with compile time
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* evaluations of constants.
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*/
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static inline __attribute_const__ int get_order(unsigned long size)
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{
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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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}
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_GENERIC_GETORDER_H */
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