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SubjectRe: [PATCH 7/9] mm: split page table lock
Hugh Dickins writes:

[...]

> + * When freeing, reset page->mapping so free_pages_check won't complain.
> + */
> +#define __pte_lockptr(page) ((spinlock_t *)&((page)->private))
> +#define pte_lock_init(_page) do { \
> + BUILD_BUG_ON((size_t)(__pte_lockptr((struct page *)0) + 1) > \
> + sizeof(struct page)); \
> + spin_lock_init(__pte_lockptr(_page)); \
> +} while (0)

Looking at this, I think BUILD_BUG_ON() should be defined in a way that
allows it to be used outside of function scope too (see patch below,
compile-tested).

Nikita.
--
Fix comment describing BUILD_BUG_ON: BUG_ON is not an assertion
(unfortunately).

Also implement BUILD_BUG_ON in a way that can be used outside of a function
scope, so that compile time checks can be placed in convenient places (like in
a header, close to the definition of related constants and data-types).

Signed-off-by: Nikita Danilov <nikita@clusterfs.com>

include/linux/kernel.h | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff -puN include/linux/kernel.h~BUILD_BUG_ON-fix-comment include/linux/kernel.h
--- git-linux/include/linux/kernel.h~BUILD_BUG_ON-fix-comment 2005-10-23 20:09:33.000000000 +0400
+++ git-linux-nikita/include/linux/kernel.h 2005-10-23 20:44:03.000000000 +0400
@@ -307,8 +307,9 @@ struct sysinfo {
char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
};

-/* Force a compilation error if condition is false */
-#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
+/* Force a compilation error if condition is true */
+#define BUILD_BUG_ON(x) \
+ void __dummy_build_bug_on(int __compile_time_assertion_failed_[-!!(x)])

#ifdef CONFIG_SYSCTL
extern int randomize_va_space;
_
-
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