Re: [RFC][PATCH 3/9] actual generic PAGE_SIZE infrastructure

[Qi Yong]

Dave Hansen wrote:

> * Add _ALIGN_UP() which we'll use now and _ALIGN_DOWN(), just for
>  parity.
> * Define ASM_CONST() macro to help using constants in both assembly
>  and C code.  Several architectures have some form of this, and
>  they will be consolidated around this one.
> * Actually create PAGE_SHIFT and PAGE_SIZE macros
> * For now, require that architectures enable GENERIC_PAGE_SIZE in
>  order to get this new code.  This option will be removed by the
>  last patch in the series, and makes the series bisect-safe.
> * Note that this moves the compiler.h define outside of the
>  #ifdef __KERNEL__, but that's OK because it has its own.
>
> Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx>
> ---
>
> threadalloc-dave/include/asm-generic/page.h |   31 ++++++++++++++++++--
> threadalloc-dave/mm/Kconfig                 |   43 ++++++++++++++++++++++++++++
> 2 files changed, 71 insertions(+), 3 deletions(-)
>
> diff -puN include/asm-generic/page.h~generic-PAGE_SIZE-infrastructure include/asm-generic/page.h
> --- threadalloc/include/asm-generic/page.h~generic-PAGE_SIZE-infrastructure	2006-08-30 15:15:00.000000000 -0700
> +++ threadalloc-dave/include/asm-generic/page.h	2006-08-30 15:15:01.000000000 -0700
> @@ -1,11 +1,36 @@
> #ifndef _ASM_GENERIC_PAGE_H
> #define _ASM_GENERIC_PAGE_H
>
> +#include <linux/compiler.h>
> +#include <linux/align.h>
> +
> #ifdef __KERNEL__
> -#ifndef __ASSEMBLY__
>
> -#include <linux/compiler.h>
> +#ifdef __ASSEMBLY__
> +#define ASM_CONST(x) x
> +#else
> +#define __ASM_CONST(x) x##UL
> +#define ASM_CONST(x) __ASM_CONST(x)
> +#endif
> +
> +#ifdef CONFIG_ARCH_GENERIC_PAGE_SIZE
> +
> +#define PAGE_SHIFT      CONFIG_PAGE_SHIFT
> +#define PAGE_SIZE       (ASM_CONST(1) << PAGE_SHIFT)
>  

Your generic page.h hides PAGE_SIZE under "#ifdef __KERNEL__".
That would cause severe userland compile failures.

Most archs have PAGE_SIZE visible to userland.
Please keep PAGE_SIZE and its friends outside "#ifdef __KERNEL__".


-- qiyong

> +
> +/*
> + * Subtle: (1 << PAGE_SHIFT) is an int, not an unsigned long. So if we
> + * assign PAGE_MASK to a larger type it gets extended the way we want
> + * (i.e. with 1s in the high bits)
> + */
> +#define PAGE_MASK      (~((1 << PAGE_SHIFT) - 1))
>
> +/* to align the pointer to the (next) page boundary */
> +#define PAGE_ALIGN(addr)        ALIGN(addr, PAGE_SIZE)
> +
> +#endif /* CONFIG_ARCH_GENERIC_PAGE_SIZE */
> +
> +#ifndef __ASSEMBLY__
> #ifndef CONFIG_ARCH_HAVE_GET_ORDER
> /* Pure 2^n version of get_order */
> static __inline__ __attribute_const__ int get_order(unsigned long size)
> @@ -22,7 +47,7 @@ static __inline__ __attribute_const__ in
> }
>
> #endif	/* CONFIG_ARCH_HAVE_GET_ORDER */
> -#endif /*  __ASSEMBLY__ */
> +#endif  /* __ASSEMBLY__ */
> #endif	/* __KERNEL__ */
>
> #endif	/* _ASM_GENERIC_PAGE_H */
>  
--
Qi Yong

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