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Date:   Tue, 9 Feb 2021 12:50:14 -0800
From:   Roman Gushchin <guro@fb.com>
To:     Yang Shi <shy828301@gmail.com>
CC:     <ktkhai@virtuozzo.com>, <vbabka@suse.cz>, <shakeelb@google.com>,
        <david@fromorbit.com>, <hannes@cmpxchg.org>, <mhocko@suse.com>,
        <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [v7 PATCH 05/12] mm: memcontrol: rename shrinker_map to
 shrinker_info
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On Tue, Feb 09, 2021 at 09:46:39AM -0800, Yang Shi wrote:
> The following patch is going to add nr_deferred into shrinker_map, the change will
> make shrinker_map not only include map anymore, so rename it to "memcg_shrinker_info".
> And this should make the patch adding nr_deferred cleaner and readable and make
> review easier.  Also remove the "memcg_" prefix.
> 
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
>  include/linux/memcontrol.h |  8 ++---
>  mm/memcontrol.c            |  6 ++--
>  mm/vmscan.c                | 62 +++++++++++++++++++-------------------
>  3 files changed, 38 insertions(+), 38 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 1739f17e0939..4c9253896e25 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -96,7 +96,7 @@ struct lruvec_stat {
>   * Bitmap of shrinker::id corresponding to memcg-aware shrinkers,
>   * which have elements charged to this memcg.
>   */
> -struct memcg_shrinker_map {
> +struct shrinker_info {
>  	struct rcu_head rcu;
>  	unsigned long map[];
>  };
> @@ -118,7 +118,7 @@ struct mem_cgroup_per_node {
>  
>  	struct mem_cgroup_reclaim_iter	iter;
>  
> -	struct memcg_shrinker_map __rcu	*shrinker_map;
> +	struct shrinker_info __rcu	*shrinker_info;

Nice!

I really like how it looks now in comparison to the v1. Thank you for
working on it!

>  
>  	struct rb_node		tree_node;	/* RB tree node */
>  	unsigned long		usage_in_excess;/* Set to the value by which */
> @@ -1581,8 +1581,8 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
>  	return false;
>  }
>  
> -int alloc_shrinker_maps(struct mem_cgroup *memcg);
> -void free_shrinker_maps(struct mem_cgroup *memcg);
> +int alloc_shrinker_info(struct mem_cgroup *memcg);
> +void free_shrinker_info(struct mem_cgroup *memcg);
>  void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id);
>  #else
>  #define mem_cgroup_sockets_enabled 0
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f5c9a0d2160b..f64ad0d044d9 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5246,11 +5246,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>  
>  	/*
> -	 * A memcg must be visible for expand_shrinker_maps()
> +	 * A memcg must be visible for expand_shrinker_info()
>  	 * by the time the maps are allocated. So, we allocate maps
>  	 * here, when for_each_mem_cgroup() can't skip it.
>  	 */
> -	if (alloc_shrinker_maps(memcg)) {
> +	if (alloc_shrinker_info(memcg)) {
>  		mem_cgroup_id_remove(memcg);
>  		return -ENOMEM;
>  	}
> @@ -5314,7 +5314,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
>  	vmpressure_cleanup(&memcg->vmpressure);
>  	cancel_work_sync(&memcg->high_work);
>  	mem_cgroup_remove_from_trees(memcg);
> -	free_shrinker_maps(memcg);
> +	free_shrinker_info(memcg);
>  	memcg_free_kmem(memcg);
>  	mem_cgroup_free(memcg);
>  }
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 641077b09e5d..9436f9246d32 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -190,20 +190,20 @@ static int shrinker_nr_max;
>  #define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \
>  	(DIV_ROUND_UP(nr_max, BITS_PER_LONG) * sizeof(unsigned long))
>  
> -static void free_shrinker_map_rcu(struct rcu_head *head)
> +static void free_shrinker_info_rcu(struct rcu_head *head)
>  {
> -	kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> +	kvfree(container_of(head, struct shrinker_info, rcu));
>  }
>  
> -static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> +static int expand_one_shrinker_info(struct mem_cgroup *memcg,
>  				   int size, int old_size)
>  {
> -	struct memcg_shrinker_map *new, *old;
> +	struct shrinker_info *new, *old;
>  	int nid;
>  
>  	for_each_node(nid) {
>  		old = rcu_dereference_protected(
> -			mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
> +			mem_cgroup_nodeinfo(memcg, nid)->shrinker_info, true);
>  		/* Not yet online memcg */
>  		if (!old)
>  			return 0;
> @@ -216,17 +216,17 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>  		memset(new->map, (int)0xff, old_size);
>  		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);
> +		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, new);
> +		call_rcu(&old->rcu, free_shrinker_info_rcu);

Why not use kvfree_rcu() and get rid of free_shrinker_info_rcu() callback?

Aside from this minor thing, the patch looks good to me. Please, feel free to add
Acked-by: Roman Gushchin <guro@fb.com>

Thanks!