[PATCH] mm: never ClearPageLRU released pages
If vmscan finds a zero refcount page on the lru list, never ClearPageLRU
it. This means the release code need not hold ->lru_lock to stabilise
PageLRU, so that lock may be skipped entirely when releasing !PageLRU pages
(because we know PageLRU won't have been temporarily cleared by vmscan,
which was previously guaranteed by holding the lock to synchronise against
vmscan).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/swap.c b/mm/swap.c
index b524ea9..3045a0f 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -209,19 +209,18 @@
*/
void fastcall __page_cache_release(struct page *page)
{
- unsigned long flags;
- struct zone *zone = page_zone(page);
+ if (PageLRU(page)) {
+ unsigned long flags;
+ struct zone *zone = page_zone(page);
- spin_lock_irqsave(&zone->lru_lock, flags);
- if (TestClearPageLRU(page))
+ spin_lock_irqsave(&zone->lru_lock, flags);
+ if (!TestClearPageLRU(page))
+ BUG();
del_page_from_lru(zone, page);
- if (page_count(page) != 0)
- page = NULL;
- spin_unlock_irqrestore(&zone->lru_lock, flags);
- if (page)
- free_hot_page(page);
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
+ }
+ free_hot_page(page);
}
-
EXPORT_SYMBOL(__page_cache_release);
/*
@@ -245,7 +244,6 @@
pagevec_init(&pages_to_free, cold);
for (i = 0; i < nr; i++) {
struct page *page = pages[i];
- struct zone *pagezone;
if (unlikely(PageCompound(page))) {
if (zone) {
@@ -259,23 +257,27 @@
if (!put_page_testzero(page))
continue;
- pagezone = page_zone(page);
- if (pagezone != zone) {
- if (zone)
- spin_unlock_irq(&zone->lru_lock);
- zone = pagezone;
- spin_lock_irq(&zone->lru_lock);
- }
- if (TestClearPageLRU(page))
- del_page_from_lru(zone, page);
- if (page_count(page) == 0) {
- if (!pagevec_add(&pages_to_free, page)) {
- spin_unlock_irq(&zone->lru_lock);
- __pagevec_free(&pages_to_free);
- pagevec_reinit(&pages_to_free);
- zone = NULL; /* No lock is held */
+ if (PageLRU(page)) {
+ struct zone *pagezone = page_zone(page);
+ if (pagezone != zone) {
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = pagezone;
+ spin_lock_irq(&zone->lru_lock);
}
+ if (!TestClearPageLRU(page))
+ BUG();
+ del_page_from_lru(zone, page);
}
+
+ if (!pagevec_add(&pages_to_free, page)) {
+ if (zone) {
+ spin_unlock_irq(&zone->lru_lock);
+ zone = NULL;
+ }
+ __pagevec_free(&pages_to_free);
+ pagevec_reinit(&pages_to_free);
+ }
}
if (zone)
spin_unlock_irq(&zone->lru_lock);
