Messages in this thread | | | Date | Tue, 19 Sep 2006 00:30:31 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 5/7] Alter get_order() so that it can make use of ilog2() on a constant [try #3] |
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On Wed, 13 Sep 2006 19:35:31 +0100 David Howells <dhowells@redhat.com> wrote:
> From: David Howells <dhowells@redhat.com> > > 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> > --- > > include/asm-generic/page.h | 14 -------------- > include/linux/log2.h | 45 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 45 insertions(+), 14 deletions(-) > > diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h > index a96b5d9..a7e374e 100644 > --- a/include/asm-generic/page.h > +++ b/include/asm-generic/page.h > @@ -6,20 +6,6 @@ #ifndef __ASSEMBLY__ > > #include <linux/compiler.h> > > -/* Pure 2^n version of get_order */ > -static __inline__ __attribute_const__ int get_order(unsigned long size) > -{ > - int order; > - > - size = (size - 1) >> (PAGE_SHIFT - 1); > - order = -1; > - do { > - size >>= 1; > - order++; > - } while (size); > - return order; > -} > - > #endif /* __ASSEMBLY__ */ > #endif /* __KERNEL__ */ > > diff --git a/include/linux/log2.h b/include/linux/log2.h > index 6ce81b7..88b7b0e 100644 > --- a/include/linux/log2.h > +++ b/include/linux/log2.h > @@ -25,6 +25,7 @@ int ____ilog2_NaN(void); > * non-constant log of base 2 calculators > * - the arch may override these in asm/bitops.h if they can be implemented > * more efficiently than using fls() and fls64() > + * - the arch is not required to handle n==0 if implementing the fallback > */ > #ifndef ARCH_HAS_ILOG2_U32 > static inline __attribute__((const)) > @@ -42,6 +43,36 @@ int __ilog2_u64(u64 n) > } > #endif > > +/* > + * 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
This breaks ia64:
In file included from include/asm/ptrace.h:234, from include/asm/processor.h:19, from include/linux/prefetch.h:14, from include/linux/list.h:8, from include/linux/wait.h:22, from include/linux/fs.h:266, from init/do_mounts_initrd.c:3: include/asm/page.h:165: error: syntax error before '?' token include/asm/page.h:170: warning: type defaults to `int' in declaration of `order' include/asm/page.h:170: error: conflicting types for 'order' include/asm/page.h:168: error: previous declaration of 'order' was here include/asm/page.h:170: error: braced-group within expression allowed only inside a function include/asm/page.h:170: warning: type defaults to `int' in declaration of `ia64_intri_res'
But for some reason putting ARCH_HAS_GET_ORDER into include/asm-ia64/bitops.h and including linux/log2.h in include/asm-ia64/page.h doesn't fix it.
I didn't pursue it further, because sprinkling ARCH_HAS_FOO things into bitops.h(!) is all rather hacky. Better to use CONFIG_* so they're always visible and one knows where to go to find things.
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