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