diff options
author | Nick Piggin <npiggin@suse.de> | 2006-03-22 08:08:03 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-22 15:53:57 (GMT) |
commit | 7c8ee9a86340db686cd4314e9944dc9b6111bda9 (patch) | |
tree | 80638e1658556b4fd7c0b92d571aaac854245bd3 /mm/vmscan.c | |
parent | f205b2fe62d321403525065a4cb31b6bff1bbe53 (diff) | |
download | linux-fsl-qoriq-7c8ee9a86340db686cd4314e9944dc9b6111bda9.tar.xz |
[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 'mm/vmscan.c')
-rw-r--r-- | mm/vmscan.c | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 8e477b1a..e21bab4 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1083,29 +1083,26 @@ static int isolate_lru_pages(int nr_to_scan, struct list_head *src, int scan = 0; while (scan++ < nr_to_scan && !list_empty(src)) { + struct list_head *target; page = lru_to_page(src); prefetchw_prev_lru_page(page, src, flags); BUG_ON(!PageLRU(page)); list_del(&page->lru); - if (unlikely(get_page_testone(page))) { + target = src; + if (likely(get_page_unless_zero(page))) { /* - * It is being freed elsewhere + * Be careful not to clear PageLRU until after we're + * sure the page is not being freed elsewhere -- the + * page release code relies on it. */ - __put_page(page); - list_add(&page->lru, src); - continue; - } + ClearPageLRU(page); + target = dst; + nr_taken++; + } /* else it is being freed elsewhere */ - /* - * Be careful not to clear PageLRU until after we're sure - * the page is not being freed elsewhere -- the page release - * code relies on it. - */ - ClearPageLRU(page); - list_add(&page->lru, dst); - nr_taken++; + list_add(&page->lru, target); } *scanned = scan; |