Re: [PATCH 29/29] mm: shrinker: move shrinker-related code into a separate file

Sergey Senozhatsky
2023-06-23T05:26:10Z

On (23/06/22 16:53), Qi Zheng wrote:
> +/*
> + * Remove one
> + */
> +void unregister_shrinker(struct shrinker *shrinker)
> +{
> + struct dentry *debugfs_entry;
> + int debugfs_id;
> +
> + if (!(shrinker->flags & SHRINKER_REGISTERED))
> + return;
> +
> + shrinker_put(shrinker);
> + wait_for_completion(&shrinker->completion_wait);
> +
> + mutex_lock(&shrinker_mutex);
> + list_del_rcu(&shrinker->list);

Should this function wait for RCU grace period(s) before it goes
touching shrinker fields?

> + shrinker->flags &= ~SHRINKER_REGISTERED;
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> + unregister_memcg_shrinker(shrinker);
> + debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
> + mutex_unlock(&shrinker_mutex);
> +
> + shrinker_debugfs_remove(debugfs_entry, debugfs_id);
> +
> + kfree(shrinker->nr_deferred);
> + shrinker->nr_deferred = NULL;
> +}
> +EXPORT_SYMBOL(unregister_shrinker);

[..]

> +void shrinker_free(struct shrinker *shrinker)
> +{
> + kfree(shrinker);
> +}
> +EXPORT_SYMBOL(shrinker_free);
> +
> +void unregister_and_free_shrinker(struct shrinker *shrinker)
> +{
> + unregister_shrinker(shrinker);
> + kfree_rcu(shrinker, rcu);
> +}

Seems like this

unregister_shrinker();
shrinker_free();

is not exact equivalent of this

unregister_and_free_shrinker();