linux-kernel - Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call

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Message-ID: <CALvZod75fge=B9LNg_sxbCiwDZjjtn8A9Q2HzU_R6rcg551o6Q@mail.gmail.com>
Date:   Sun, 7 Mar 2021 22:13:04 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Yang Shi <shy828301@...il.com>, paulmck@...nel.org
Cc:     Roman Gushchin <guro@...com>, Kirill Tkhai <ktkhai@...tuozzo.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Chinner <david@...morbit.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu

On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@...il.com> wrote:
>
> Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> We don't have to define a dedicated callback for call_rcu() anymore.
>
> Signed-off-by: Yang Shi <shy828301@...il.com>
> ---
>  mm/vmscan.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2e753c2516fa..c2a309acd86b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
>         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
>  }
>
> -static void free_shrinker_map_rcu(struct rcu_head *head)
> -{
> -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> -}
> -
>  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>                                    int size, int old_size)
>  {
> @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>                 memset((void *)new->map + old_size, 0, size - old_size);
>
>                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> +               kvfree_rcu(old);

Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
param can call synchronize_rcu().