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

[Qi Zheng via Linux-erofs]

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.a...@bytedance.com>
Reviewed-by: Muchun Song <songmuc...@bytedance.com>
---
 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