Fix and Enhance deactive_page

A few days ago, Ying reported a problem.
http://marc.info/?l=linux-mm&m=130403310601663&w=2
After I and Ying dive in problem, We found deactive_page has a problem. Apparently, It's a BUG so
[1/2] is fix of the problem and [2/2] is enhancement for helping CPU.

* v2
- add Reviewed-by signs
- Fix typo

Minchan Kim (2):
[1/2] Check PageUnevictable in lru_deactivate_fn [2/2] Filter unevictable page out in deactivate_page

 mm/swap.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

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The lru_deactivate_fn should not move page which in on unevictable lru into inactive list. Otherwise, we can meet BUG when we use isolate_lru_pages as __isolate_lru_page could return -EINVAL.
It's really BUG and let's fix it.

---
 mm/swap.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

index a83ec5a..2e9656d 100644
@@ -429,6 +429,9 @@ static void lru_deactivate_fn(struct page *page, void *arg)
 	if (!PageLRU(page))
 		return;
 
+	if (PageUnevictable(page))
+		return;
+
 	/* Some processes are using the page */
 	if (page_mapped(page))
 		return;

1.7.1

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It's pointless that deactive_page's pagevec operation about unevictable page as it's nop.
This patch removes unnecessary overhead which might be a bit problem in case that there are many unevictable page in system(ex, mprotect workload)

---
 mm/swap.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

index 2e9656d..e121ceb 100644
@@ -511,6 +511,15 @@ static void drain_cpu_pagevecs(int cpu)
  */
 void deactivate_page(struct page *page)
 {
+
+	/*
+	 * In workload which system has many unevictable page(ex, mprotect),
+	 * unevictable page deactivation for accelerating reclaim
+	 * is pointless.
+	 */
+	if (PageUnevictable(page))
+		return;
+
 	if (likely(get_page_unless_zero(page))) {
 		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 

1.7.1

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