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

Qi Zheng
2023-06-22T09:03:02Z

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@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