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

[Sergey Senozhatsky <senozhatsky@chromium.org>]

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();

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