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Subject: [PATCH RFC 03/10] mm: Convert shrinker_rwsem to mutex
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
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Date:   Tue, 07 Aug 2018 18:38:00 +0300
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There are no readers, so rwsem is not need anymore.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 mm/vmscan.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9dda903a1406..2dc274a385b9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -167,7 +167,7 @@ int vm_swappiness = 60;
 unsigned long vm_total_pages;
 
 static LIST_HEAD(shrinker_list);
-static DECLARE_RWSEM(shrinker_rwsem);
+static DEFINE_MUTEX(shrinker_mutex);
 DEFINE_STATIC_SRCU(srcu);
 
 #ifdef CONFIG_MEMCG_KMEM
@@ -192,7 +192,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 {
 	int id, ret = -ENOMEM;
 
-	down_write(&shrinker_rwsem);
+	mutex_lock(&shrinker_mutex);
 	id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
 	if (id < 0)
 		goto unlock;
@@ -208,7 +208,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 	shrinker->id = id;
 	ret = 0;
 unlock:
-	up_write(&shrinker_rwsem);
+	mutex_unlock(&shrinker_mutex);
 	return ret;
 }
 
@@ -218,9 +218,9 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
 
 	BUG_ON(id < 0);
 
-	down_write(&shrinker_rwsem);
+	mutex_lock(&shrinker_mutex);
 	idr_remove(&shrinker_idr, id);
-	up_write(&shrinker_rwsem);
+	mutex_unlock(&shrinker_mutex);
 }
 #else /* CONFIG_MEMCG_KMEM */
 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
@@ -405,10 +405,10 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
 
 void register_shrinker_prepared(struct shrinker *shrinker)
 {
-	down_write(&shrinker_rwsem);
+	mutex_lock(&shrinker_mutex);
 	list_add_tail_rcu(&shrinker->list, &shrinker_list);
 	idr_replace(&shrinker_idr, shrinker, shrinker->id);
-	up_write(&shrinker_rwsem);
+	mutex_unlock(&shrinker_mutex);
 }
 
 int register_shrinker(struct shrinker *shrinker)
@@ -431,9 +431,9 @@ void unregister_shrinker(struct shrinker *shrinker)
 		return;
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		unregister_memcg_shrinker(shrinker);
-	down_write(&shrinker_rwsem);
+	mutex_lock(&shrinker_mutex);
 	list_del_rcu(&shrinker->list);
-	up_write(&shrinker_rwsem);
+	mutex_unlock(&shrinker_mutex);
 
 	synchronize_srcu(&srcu);