linux-kernel - Re: [PATCH v1 6/6] mm/list_lru.c: remove kvfree_rcu

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Date:   Mon, 16 Mar 2020 11:49:55 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        RCU <rcu@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH v1 6/6] mm/list_lru.c: remove kvfree_rcu_local() function

On Sun, Mar 15, 2020 at 07:18:40PM +0100, Uladzislau Rezki (Sony) wrote:
> Since there is newly introduced kvfree_rcu() API,
> there is no need in queuing and using call_rcu()
> to kvfree() an object after the GP.
> 
> Remove kvfree_rcu_local() function and replace
> call_rcu() by new kvfree_rcu() API that does
> the same but in more efficient way.

This patch LGTM:
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  mm/list_lru.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 386424688f80..69becdb22408 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -12,6 +12,7 @@
>  #include <linux/slab.h>
>  #include <linux/mutex.h>
>  #include <linux/memcontrol.h>
> +#include <linux/rcupdate.h>
>  #include "slab.h"
>  
>  #ifdef CONFIG_MEMCG_KMEM
> @@ -383,21 +384,13 @@ static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
>  	struct list_lru_memcg *memcg_lrus;
>  	/*
>  	 * This is called when shrinker has already been unregistered,
> -	 * and nobody can use it. So, there is no need to use kvfree_rcu_local().
> +	 * and nobody can use it. So, there is no need to use kvfree_rcu().
>  	 */
>  	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
>  	__memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
>  	kvfree(memcg_lrus);
>  }
>  
> -static void kvfree_rcu_local(struct rcu_head *head)
> -{
> -	struct list_lru_memcg *mlru;
> -
> -	mlru = container_of(head, struct list_lru_memcg, rcu);
> -	kvfree(mlru);
> -}
> -
>  static int memcg_update_list_lru_node(struct list_lru_node *nlru,
>  				      int old_size, int new_size)
>  {
> @@ -429,7 +422,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
>  	rcu_assign_pointer(nlru->memcg_lrus, new);
>  	spin_unlock_irq(&nlru->lock);
>  
> -	call_rcu(&old->rcu, kvfree_rcu_local);
> +	kvfree_rcu(old, rcu);
>  	return 0;
>  }
>  
> -- 
> 2.20.1
>