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

From: Qi Yong
Date: Tue Oct 17 2006 - 03:13:08 EST


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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