[PATCH 20/29] zsmalloc: dynamically allocate the mm-zspool shrinker

[Qi Zheng]

In preparation for implementing lockless slab shrink,
we need 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 at bytedance.com>
---
 mm/zsmalloc.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3f057970504e..c03b34ae637e 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;
@@ -2107,8 +2107,7 @@ 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.
@@ -2126,8 +2125,7 @@ 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];
@@ -2142,18 +2140,24 @@ static unsigned long zs_shrinker_count(struct shrinker *shrinker,
 
 static void zs_unregister_shrinker(struct zs_pool *pool)
 {
-	unregister_shrinker(&pool->shrinker);
+	unregister_and_free_shrinker(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;
+	int ret;
+
+	pool->shrinker = shrinker_alloc_and_init(zs_shrinker_count,
+						 zs_shrinker_scan, 0,
+						 DEFAULT_SEEKS, 0, pool);
+	if (!pool->shrinker)
+		return -ENOMEM;
 
-	return register_shrinker(&pool->shrinker, "mm-zspool:%s",
-				 pool->name);
+	ret = register_shrinker(pool->shrinker, "mm-zspool:%s", pool->name);
+	if (ret)
+		shrinker_free(pool->shrinker);
+
+	return ret;
 }
 
 static int calculate_zspage_chain_size(int class_size)
-- 
2.30.2