[PATCH v4 32/48] mbcache: dynamically allocate the mbcache shrinker

From: Qi Zheng
Date: Mon Aug 07 2023 - 07:19:54 EST


In preparation for implementing lockless slab shrink, use new APIs 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@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
fs/mbcache.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/fs/mbcache.c b/fs/mbcache.c
index 2a4b8b549e93..0d1e24e9a5e3 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 +332,7 @@ 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);
}

@@ -377,15 +375,20 @@ struct mb_cache *mb_cache_create(int bucket_bits)
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")) {
+ cache->c_shrink = shrinker_alloc(0, "mbcache-shrinker");
+ if (!cache->c_shrink) {
kfree(cache->c_hash);
kfree(cache);
goto err_out;
}

+ cache->c_shrink->count_objects = mb_cache_count;
+ cache->c_shrink->scan_objects = mb_cache_scan;
+ cache->c_shrink->seeks = DEFAULT_SEEKS;
+ cache->c_shrink->private_data = cache;
+
+ shrinker_register(cache->c_shrink);
+
INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);

return cache;
@@ -406,7 +409,7 @@ void mb_cache_destroy(struct mb_cache *cache)
{
struct mb_cache_entry *entry, *next;

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

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