[PATCH 3/3] mm: list_lru: Add lock_irq member to __list_lru_init()

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

scan_shadow_nodes() is the only user of __list_lru_walk_one() which
disables interrupts before invoking it. The reason is that nlru->lock is
nesting inside IRQ-safe i_pages lock. Some functions unconditionally
acquire the lock with the _irq() suffix.

__list_lru_walk_one() can't acquire the lock unconditionally with _irq()
suffix because it might invoke a callback which unlocks the nlru->lock
and invokes a sleeping function without enabling interrupts.

Add an argument to __list_lru_init() which identifies wheather the
nlru->lock needs to be acquired with disabling interrupts or without.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/list_lru.h | 12 ++++++++----
 mm/list_lru.c            | 14 ++++++++++----
 mm/workingset.c          | 12 ++++--------
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 96def9d15b1b..c2161c3a1809 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -51,18 +51,22 @@ struct list_lru_node {
 
 struct list_lru {
 	struct list_lru_node	*node;
+	bool			lock_irq;
 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
 	struct list_head	list;
 #endif
 };
 
 void list_lru_destroy(struct list_lru *lru);
-int __list_lru_init(struct list_lru *lru, bool memcg_aware,
+int __list_lru_init(struct list_lru *lru, bool memcg_aware, bool lock_irq,
 		    struct lock_class_key *key);
 
-#define list_lru_init(lru)		__list_lru_init((lru), false, NULL)
-#define list_lru_init_key(lru, key)	__list_lru_init((lru), false, (key))
-#define list_lru_init_memcg(lru)	__list_lru_init((lru), true, NULL)
+#define list_lru_init(lru)		__list_lru_init((lru), false, false, \
+							NULL)
+#define list_lru_init_key(lru, key)	__list_lru_init((lru), false, false, \
+							(key))
+#define list_lru_init_memcg(lru)	__list_lru_init((lru), true, false, \
+							NULL)
 
 int memcg_update_all_list_lrus(int num_memcgs);
 void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
diff --git a/mm/list_lru.c b/mm/list_lru.c
index fcfb6c89ed47..1c49d48078e4 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -204,7 +204,10 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
 	struct list_head *item, *n;
 	unsigned long isolated = 0;
 
-	spin_lock(&nlru->lock);
+	if (lru->lock_irq)
+		spin_lock_irq(&nlru->lock);
+	else
+		spin_lock(&nlru->lock);
 	l = list_lru_from_memcg_idx(nlru, memcg_idx);
 restart:
 	list_for_each_safe(item, n, &l->list) {
@@ -251,7 +254,10 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
 		}
 	}
 
-	spin_unlock(&nlru->lock);
+	if (lru->lock_irq)
+		spin_unlock_irq(&nlru->lock);
+	else
+		spin_unlock(&nlru->lock);
 	return isolated;
 }
 
@@ -553,7 +559,7 @@ static void memcg_destroy_list_lru(struct list_lru *lru)
 }
 #endif /* CONFIG_MEMCG && !CONFIG_SLOB */
 
-int __list_lru_init(struct list_lru *lru, bool memcg_aware,
+int __list_lru_init(struct list_lru *lru, bool memcg_aware, bool lock_irq,
 		    struct lock_class_key *key)
 {
 	int i;
@@ -580,7 +586,7 @@ int __list_lru_init(struct list_lru *lru, bool memcg_aware,
 		lru->node = NULL;
 		goto out;
 	}
-
+	lru->lock_irq = lock_irq;
 	list_lru_register(lru);
 out:
 	memcg_put_cache_ids();
diff --git a/mm/workingset.c b/mm/workingset.c
index 529480c21f93..23ce00f48212 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -480,13 +480,8 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
 static unsigned long scan_shadow_nodes(struct shrinker *shrinker,
 				       struct shrink_control *sc)
 {
-	unsigned long ret;
-
-	/* list_lru lock nests inside the IRQ-safe i_pages lock */
-	local_irq_disable();
-	ret = list_lru_shrink_walk(&shadow_nodes, sc, shadow_lru_isolate, NULL);
-	local_irq_enable();
-	return ret;
+	return list_lru_shrink_walk(&shadow_nodes, sc, shadow_lru_isolate,
+				    NULL);
 }
 
 static struct shrinker workingset_shadow_shrinker = {
@@ -523,7 +518,8 @@ static int __init workingset_init(void)
 	pr_info("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n",
 	       timestamp_bits, max_order, bucket_order);
 
-	ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key);
+	/* list_lru lock nests inside the IRQ-safe i_pages lock */
+	ret = __list_lru_init(&shadow_nodes, true, true, &shadow_nodes_key);
 	if (ret)
 		goto err;
 	ret = register_shrinker(&workingset_shadow_shrinker);
-- 
2.18.0