From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:29:51 -0500
Subject: mm: convert swap to percpu locked
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.10/patches-3.10.4-rt1.tar.xz

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 mm/swap.c |   30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

Index: linux-stable/mm/swap.c
===================================================================
--- linux-stable.orig/mm/swap.c
+++ linux-stable/mm/swap.c
@@ -31,6 +31,7 @@
 #include <linux/memcontrol.h>
 #include <linux/gfp.h>
 #include <linux/uio.h>
+#include <linux/locallock.h>
 
 #include "internal.h"
 
@@ -41,6 +42,9 @@ static DEFINE_PER_CPU(struct pagevec[NR_
 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
 
+static DEFINE_LOCAL_IRQ_LOCK(rotate_lock);
+static DEFINE_LOCAL_IRQ_LOCK(swapvec_lock);
+
 /*
  * This path almost never happens for VM activity - pages are normally
  * freed via pagevecs.  But it gets used by networking.
@@ -355,11 +359,11 @@ void rotate_reclaimable_page(struct page
 		unsigned long flags;
 
 		page_cache_get(page);
-		local_irq_save(flags);
+		local_lock_irqsave(rotate_lock, flags);
 		pvec = &__get_cpu_var(lru_rotate_pvecs);
 		if (!pagevec_add(pvec, page))
 			pagevec_move_tail(pvec);
-		local_irq_restore(flags);
+		local_unlock_irqrestore(rotate_lock, flags);
 	}
 }
 
@@ -404,12 +408,13 @@ static void activate_page_drain(int cpu)
 void activate_page(struct page *page)
 {
 	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
-		struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
+		struct pagevec *pvec = &get_locked_var(swapvec_lock,
+						       activate_page_pvecs);
 
 		page_cache_get(page);
 		if (!pagevec_add(pvec, page))
 			pagevec_lru_move_fn(pvec, __activate_page, NULL);
-		put_cpu_var(activate_page_pvecs);
+		put_locked_var(swapvec_lock, activate_page_pvecs);
 	}
 }
 
@@ -457,13 +462,13 @@ EXPORT_SYMBOL(mark_page_accessed);
  */
 void __lru_cache_add(struct page *page, enum lru_list lru)
 {
-	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
+	struct pagevec *pvec = &get_locked_var(swapvec_lock, lru_add_pvecs)[lru];
 
 	page_cache_get(page);
 	if (!pagevec_space(pvec))
 		__pagevec_lru_add(pvec, lru);
 	pagevec_add(pvec, page);
-	put_cpu_var(lru_add_pvecs);
+	put_locked_var(swapvec_lock, lru_add_pvecs);
 }
 EXPORT_SYMBOL(__lru_cache_add);
 
@@ -598,9 +603,9 @@ void lru_add_drain_cpu(int cpu)
 		unsigned long flags;
 
 		/* No harm done if a racing interrupt already did this */
-		local_irq_save(flags);
+		local_lock_irqsave(rotate_lock, flags);
 		pagevec_move_tail(pvec);
-		local_irq_restore(flags);
+		local_unlock_irqrestore(rotate_lock, flags);
 	}
 
 	pvec = &per_cpu(lru_deactivate_pvecs, cpu);
@@ -628,18 +633,19 @@ void deactivate_page(struct page *page)
 		return;
 
 	if (likely(get_page_unless_zero(page))) {
-		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
+		struct pagevec *pvec = &get_locked_var(swapvec_lock,
+						       lru_deactivate_pvecs);
 
 		if (!pagevec_add(pvec, page))
 			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
-		put_cpu_var(lru_deactivate_pvecs);
+		put_locked_var(swapvec_lock, lru_deactivate_pvecs);
 	}
 }
 
 void lru_add_drain(void)
 {
-	lru_add_drain_cpu(get_cpu());
-	put_cpu();
+	lru_add_drain_cpu(local_lock_cpu(swapvec_lock));
+	local_unlock_cpu(swapvec_lock);
 }
 
 static void lru_add_drain_per_cpu(struct work_struct *dummy)