Messages in this thread | | | Date | Tue, 06 Mar 2007 09:58:32 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] Fix get_order() |
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David Howells wrote: > From: David Howells <dhowells@redhat.com> > > Fix get_order() to use ilog2() properly. > > Signed-Off-By: David Howells <dhowells@redhat.com> > --- > > include/asm-generic/page.h | 14 +++++++++++--- > include/linux/log2.h | 20 ++++++++++++++++++-- > 2 files changed, 29 insertions(+), 5 deletions(-) > > diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h > index b55052c..c37571d 100644 > --- a/include/asm-generic/page.h > +++ b/include/asm-generic/page.h > @@ -17,10 +17,18 @@ 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; > + int order; > + if (size <= 1) > + order = 0; > + else > + order = __ilog2_u32(size - 1) + 1 - page_shift; > return order >= 0 ? order : 0;
This seems a lot more complex than it should be.
Assuming page_shift is usually constant, it would seem to make more sense to do:
if (size <= (1UL << page_shift)) return 0; else return __ilog2_u32(size-1)+1-page_shift;
... instead of having *two* conditionals...
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