From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 29 Jan 2015 17:19:44 +0100
Subject: mm/workingset: Do not protect workingset_shadow_nodes with irq off
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

workingset_shadow_nodes is protected by local_irq_disable(). Some users
use spin_lock_irq().
Replace the irq/on with a local_lock(). Rename workingset_shadow_nodes
so I catch users of it which will be introduced later.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/swap.h |    4 +++-
 mm/filemap.c         |   11 ++++++++---
 mm/truncate.c        |    7 +++++--
 mm/workingset.c      |   23 ++++++++++++-----------
 4 files changed, 28 insertions(+), 17 deletions(-)

--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -11,6 +11,7 @@
 #include <linux/fs.h>
 #include <linux/atomic.h>
 #include <linux/page-flags.h>
+#include <linux/locallock.h>
 #include <asm/page.h>
 
 struct notifier_block;
@@ -252,7 +253,8 @@ struct swap_info_struct {
 void *workingset_eviction(struct address_space *mapping, struct page *page);
 bool workingset_refault(void *shadow);
 void workingset_activation(struct page *page);
-extern struct list_lru workingset_shadow_nodes;
+extern struct list_lru __workingset_shadow_nodes;
+DECLARE_LOCAL_IRQ_LOCK(workingset_shadow_lock);
 
 static inline unsigned int workingset_node_pages(struct radix_tree_node *node)
 {
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -169,7 +169,9 @@ static void page_cache_tree_delete(struc
 	if (!workingset_node_pages(node) &&
 	    list_empty(&node->private_list)) {
 		node->private_data = mapping;
-		list_lru_add(&workingset_shadow_nodes, &node->private_list);
+		local_lock(workingset_shadow_lock);
+		list_lru_add(&__workingset_shadow_nodes, &node->private_list);
+		local_unlock(workingset_shadow_lock);
 	}
 }
 
@@ -618,9 +620,12 @@ static int page_cache_tree_insert(struct
 		 * node->private_list is protected by
 		 * mapping->tree_lock.
 		 */
-		if (!list_empty(&node->private_list))
-			list_lru_del(&workingset_shadow_nodes,
+		if (!list_empty(&node->private_list)) {
+			local_lock(workingset_shadow_lock);
+			list_lru_del(&__workingset_shadow_nodes,
 				     &node->private_list);
+			local_unlock(workingset_shadow_lock);
+		}
 	}
 	return 0;
 }
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -63,9 +63,12 @@ static void clear_exceptional_entry(stru
 		 * protected by mapping->tree_lock.
 		 */
 		if (!workingset_node_shadows(node) &&
-		    !list_empty(&node->private_list))
-			list_lru_del(&workingset_shadow_nodes,
+		    !list_empty(&node->private_list)) {
+			local_lock(workingset_shadow_lock);
+			list_lru_del(&__workingset_shadow_nodes,
 					&node->private_list);
+			local_unlock(workingset_shadow_lock);
+		}
 		__radix_tree_delete_node(&mapping->page_tree, node);
 	}
 unlock:
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -335,7 +335,8 @@ void workingset_activation(struct page *
  * point where they would still be useful.
  */
 
-struct list_lru workingset_shadow_nodes;
+struct list_lru __workingset_shadow_nodes;
+DEFINE_LOCAL_IRQ_LOCK(workingset_shadow_lock);
 
 static unsigned long count_shadow_nodes(struct shrinker *shrinker,
 					struct shrink_control *sc)
@@ -345,9 +346,9 @@ static unsigned long count_shadow_nodes(
 	unsigned long pages;
 
 	/* list_lru lock nests inside IRQ-safe mapping->tree_lock */
-	local_irq_disable();
-	shadow_nodes = list_lru_shrink_count(&workingset_shadow_nodes, sc);
-	local_irq_enable();
+	local_lock_irq(workingset_shadow_lock);
+	shadow_nodes = list_lru_shrink_count(&__workingset_shadow_nodes, sc);
+	local_unlock_irq(workingset_shadow_lock);
 
 	if (memcg_kmem_enabled())
 		pages = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
@@ -440,9 +441,9 @@ static enum lru_status shadow_lru_isolat
 	spin_unlock(&mapping->tree_lock);
 	ret = LRU_REMOVED_RETRY;
 out:
-	local_irq_enable();
+	local_unlock_irq(workingset_shadow_lock);
 	cond_resched();
-	local_irq_disable();
+	local_lock_irq(workingset_shadow_lock);
 	spin_lock(lru_lock);
 	return ret;
 }
@@ -453,10 +454,10 @@ static unsigned long scan_shadow_nodes(s
 	unsigned long ret;
 
 	/* list_lru lock nests inside IRQ-safe mapping->tree_lock */
-	local_irq_disable();
-	ret =  list_lru_shrink_walk(&workingset_shadow_nodes, sc,
+	local_lock_irq(workingset_shadow_lock);
+	ret =  list_lru_shrink_walk(&__workingset_shadow_nodes, sc,
 				    shadow_lru_isolate, NULL);
-	local_irq_enable();
+	local_unlock_irq(workingset_shadow_lock);
 	return ret;
 }
 
@@ -494,7 +495,7 @@ static int __init workingset_init(void)
 	printk("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n",
 	       timestamp_bits, max_order, bucket_order);
 
-	ret = list_lru_init_key(&workingset_shadow_nodes, &shadow_nodes_key);
+	ret = list_lru_init_key(&__workingset_shadow_nodes, &shadow_nodes_key);
 	if (ret)
 		goto err;
 	ret = register_shrinker(&workingset_shadow_shrinker);
@@ -502,7 +503,7 @@ static int __init workingset_init(void)
 		goto err_list_lru;
 	return 0;
 err_list_lru:
-	list_lru_destroy(&workingset_shadow_nodes);
+	list_lru_destroy(&__workingset_shadow_nodes);
 err:
 	return ret;
 }
