diff options
author | Nick Piggin <npiggin@suse.de> | 2006-03-22 00:08:03 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-22 07:53:57 -0800 |
commit | 7c8ee9a86340db686cd4314e9944dc9b6111bda9 (patch) | |
tree | 80638e1658556b4fd7c0b92d571aaac854245bd3 /include | |
parent | f205b2fe62d321403525065a4cb31b6bff1bbe53 (diff) |
[PATCH] mm: simplify vmscan vs release refcounting
The VM has an interesting race where a page refcount can drop to zero, but it
is still on the LRU lists for a short time. This was solved by testing a 0->1
refcount transition when picking up pages from the LRU, and dropping the
refcount in that case.
Instead, use atomic_add_unless to ensure we never pick up a 0 refcount page
from the LRU, thus a 0 refcount page will never have its refcount elevated
until it is allocated again.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/mm.h | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 498ff8778fb..b12d5c76420 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -301,17 +301,20 @@ struct page { * Drop a ref, return true if the logical refcount fell to zero (the page has * no users) */ -#define put_page_testzero(p) \ - ({ \ - BUG_ON(atomic_read(&(p)->_count) == -1);\ - atomic_add_negative(-1, &(p)->_count); \ - }) +static inline int put_page_testzero(struct page *page) +{ + BUG_ON(atomic_read(&page->_count) == -1); + return atomic_add_negative(-1, &page->_count); +} /* - * Grab a ref, return true if the page previously had a logical refcount of - * zero. ie: returns true if we just grabbed an already-deemed-to-be-free page + * Try to grab a ref unless the page has a refcount of zero, return false if + * that is the case. */ -#define get_page_testone(p) atomic_inc_and_test(&(p)->_count) +static inline int get_page_unless_zero(struct page *page) +{ + return atomic_add_unless(&page->_count, 1, -1); +} #define set_page_count(p,v) atomic_set(&(p)->_count, (v) - 1) #define __put_page(p) atomic_dec(&(p)->_count) |