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[PATCH] mm: de-skew page refcounting 

atomic_add_unless (atomic_inc_not_zero) no longer requires an offset refcount
to function correctly.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-03-22 00:08:03 -08:00 committed by Linus Torvalds
parent 7c8ee9a863
commit 8dc04efbfb
1 changed files with 5 additions and 14 deletions
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19
include/linux/mm.h
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@ -286,15 +286,6 @@ struct page {
*
* Also, many kernel routines increase the page count before a critical
* routine so they can be sure the page doesn't go away from under them.
*
* Since 2.6.6 (approx), a free page has ->_count = -1. This is so that we
* can use atomic_add_negative(-1, page->_count) to detect when the page
* becomes free and so that we can also use atomic_inc_and_test to atomically
* detect when we just tried to grab a ref on a page which some other CPU has
* already deemed to be freeable.
*
* NO code should make assumptions about this internal detail! Use the provided
* macros which retain the old rules: page_count(page) == 0 is a free page.
*/
/*
@ -303,8 +294,8 @@ struct page {
*/
static inline int put_page_testzero(struct page *page)
{
BUG_ON(atomic_read(&page->_count) == -1);
return atomic_add_negative(-1, &page->_count);
BUG_ON(atomic_read(&page->_count) == 0);
return atomic_dec_and_test(&page->_count);
}
/*
@ -313,10 +304,10 @@ static inline int put_page_testzero(struct page *page)
*/
static inline int get_page_unless_zero(struct page *page)
{
return atomic_add_unless(&page->_count, 1, -1);
return atomic_inc_not_zero(&page->_count);
}
#define set_page_count(p,v) atomic_set(&(p)->_count, (v) - 1)
#define set_page_count(p,v) atomic_set(&(p)->_count, (v))
#define __put_page(p) atomic_dec(&(p)->_count)
extern void FASTCALL(__page_cache_release(struct page *));
@ -325,7 +316,7 @@ static inline int page_count(struct page *page)
{
if (PageCompound(page))
page = (struct page *)page_private(page);
return atomic_read(&page->_count) + 1;
return atomic_read(&page->_count);
}
static inline void get_page(struct page *page)