[PATCH 12/29] mbcache: dynamically allocate the mbcache shrinker

Qi Zheng
2023-06-22T08:42:53Z

we need to dynamically allocate the mbcache 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 mb_cache.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
fs/mbcache.c | 39 +++++++++++++++++++++------------------
1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/fs/mbcache.c b/fs/mbcache.c
index 2a4b8b549e93..fec393e55a66 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -37,7 +37,7 @@ struct mb_cache {
struct list_head c_list;
/* Number of entries in cache */
unsigned long c_entry_count;
- struct shrinker c_shrink;
+ struct shrinker *c_shrink;
/* Work for shrinking when the cache has too many entries */
struct work_struct c_shrink_work;
};
@@ -293,8 +293,7 @@ EXPORT_SYMBOL(mb_cache_entry_touch);
static unsigned long mb_cache_count(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct mb_cache *cache = container_of(shrink, struct mb_cache,
- c_shrink);
+ struct mb_cache *cache = shrink->private_data;

return cache->c_entry_count;
}
@@ -333,8 +332,8 @@ static unsigned long mb_cache_shrink(struct mb_cache *cache,
static unsigned long mb_cache_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct mb_cache *cache = container_of(shrink, struct mb_cache,
- c_shrink);
+ struct mb_cache *cache = shrink->private_data;
+
return mb_cache_shrink(cache, sc->nr_to_scan);
}

@@ -370,26 +369,30 @@ struct mb_cache *mb_cache_create(int bucket_bits)
cache->c_hash = kmalloc_array(bucket_count,
sizeof(struct hlist_bl_head),
GFP_KERNEL);
- if (!cache->c_hash) {
- kfree(cache);
- goto err_out;
- }
+ if (!cache->c_hash)
+ goto err_c_hash;
+
for (i = 0; i < bucket_count; i++)
INIT_HLIST_BL_HEAD(&cache->c_hash[i]);

- cache->c_shrink.count_objects = mb_cache_count;
- cache->c_shrink.scan_objects = mb_cache_scan;
- cache->c_shrink.seeks = DEFAULT_SEEKS;
- if (register_shrinker(&cache->c_shrink, "mbcache-shrinker")) {
- kfree(cache->c_hash);
- kfree(cache);
- goto err_out;
- }
+ cache->c_shrink = shrinker_alloc_and_init(mb_cache_count, mb_cache_scan,
+ 0, DEFAULT_SEEKS, 0, cache);
+ if (!cache->c_shrink)
+ goto err_shrinker;
+
+ if (register_shrinker(cache->c_shrink, "mbcache-shrinker"))
+ goto err_register;

INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);

return cache;

+err_register:
+ shrinker_free(cache->c_shrink);
+err_shrinker:
+ kfree(cache->c_hash);
+err_c_hash:
+ kfree(cache);
err_out:
return NULL;
}
@@ -406,7 +409,7 @@ void mb_cache_destroy(struct mb_cache *cache)
{
struct mb_cache_entry *entry, *next;

- unregister_shrinker(&cache->c_shrink);
+ unregister_and_free_shrinker(cache->c_shrink);

/*
* We don't bother with any locking. Cache must not be used at this
--
2.30.2