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

Qi Yong
2006-10-17T07:29:34Z

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@us.ibm.com>
>---
>
> 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