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Commit 8dc04efb authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7c8ee9a8

include/linux/mm.h

+5 −14
Original line number Diff line number Diff line
@@ -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)