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bitops: Adjust the comment on get_order() to describe the size==0 case

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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>
This commit is contained in:
David Howells 2012-02-20 22:39:18 +00:00 • committed by H. Peter Anvin
parent 7931d49305
commit e0891a9816
1 changed files with 22 additions and 1 deletions
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23
include/asm-generic/getorder.h
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@ -5,7 +5,28 @@
#include <linux/compiler.h> #include <linux/compiler.h>
/* Pure 2^n version of get_order */ /**
* get_order - Determine the allocation order of a memory size
* @size: The size for which to get the order
*
* Determine the allocation order of a particular sized block of memory. This
* is on a logarithmic scale, where:
*
* 0 -> 2^0 * PAGE_SIZE and below
* 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
* 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
* 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
* 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
* ...
*
* The order returned is used to find the smallest allocation granule required
* to hold an object of the specified size.
*
* The result is undefined if the size is 0.
*
* This function may be used to initialise variables with compile time
* evaluations of constants.
*/
static inline __attribute_const__ int get_order(unsigned long size) static inline __attribute_const__ int get_order(unsigned long size)
{ {
int order; int order;