[PATCH v4 40/48] zsmalloc: dynamically allocate the mm-zspool shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the mm-zspool shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct zs_pool.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 mm/zsmalloc.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index b58f957429f0..1909234bb345 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -229,7 +229,7 @@ struct zs_pool {
 	struct zs_pool_stats stats;
 
 	/* Compact classes */
-	struct shrinker shrinker;
+	struct shrinker *shrinker;
 
 #ifdef CONFIG_ZSMALLOC_STAT
 	struct dentry *stat_dentry;
@@ -2086,8 +2086,7 @@ static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
 		struct shrink_control *sc)
 {
 	unsigned long pages_freed;
-	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
-			shrinker);
+	struct zs_pool *pool = shrinker->private_data;
 
 	/*
 	 * Compact classes and calculate compaction delta.
@@ -2105,8 +2104,7 @@ static unsigned long zs_shrinker_count(struct shrinker *shrinker,
 	int i;
 	struct size_class *class;
 	unsigned long pages_to_free = 0;
-	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
-			shrinker);
+	struct zs_pool *pool = shrinker->private_data;
 
 	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
 		class = pool->size_class[i];
@@ -2121,18 +2119,24 @@ static unsigned long zs_shrinker_count(struct shrinker *shrinker,
 
 static void zs_unregister_shrinker(struct zs_pool *pool)
 {
-	unregister_shrinker(&pool->shrinker);
+	shrinker_free(pool->shrinker);
 }
 
 static int zs_register_shrinker(struct zs_pool *pool)
 {
-	pool->shrinker.scan_objects = zs_shrinker_scan;
-	pool->shrinker.count_objects = zs_shrinker_count;
-	pool->shrinker.batch = 0;
-	pool->shrinker.seeks = DEFAULT_SEEKS;
+	pool->shrinker = shrinker_alloc(0, "mm-zspool:%s", pool->name);
+	if (!pool->shrinker)
+		return -ENOMEM;
+
+	pool->shrinker->scan_objects = zs_shrinker_scan;
+	pool->shrinker->count_objects = zs_shrinker_count;
+	pool->shrinker->batch = 0;
+	pool->shrinker->seeks = DEFAULT_SEEKS;
+	pool->shrinker->private_data = pool;
 
-	return register_shrinker(&pool->shrinker, "mm-zspool:%s",
-				 pool->name);
+	shrinker_register(pool->shrinker);
+
+	return 0;
 }
 
 static int calculate_zspage_chain_size(int class_size)
-- 
2.30.2