linux-kernel - Re: [PATCH 4/9] memcg: manually inline __refill

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Message-ID: <Z9jFPP7HsTzs_aW0@google.com>
Date: Tue, 18 Mar 2025 00:58:36 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 4/9] memcg: manually inline __refill_stock

On Sat, Mar 15, 2025 at 10:49:25AM -0700, Shakeel Butt wrote:
> There are no more multiple callers of __refill_stock(), so simply inline
> it to refill_stock().
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/memcontrol.c | 32 ++++++++++++--------------------
>  1 file changed, 12 insertions(+), 20 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b54e3a1d23bd..7054b0ebd207 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1865,14 +1865,21 @@ static void drain_local_stock(struct work_struct *dummy)
>  	obj_cgroup_put(old);
>  }
>  
> -/*
> - * Cache charges(val) to local per_cpu area.
> - * This will be consumed by consume_stock() function, later.
> - */
> -static void __refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
> +/* Should never be called with root_mem_cgroup. */

How about adding something like this?

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 768d6b15dbfa..5c26002f2168 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1881,6 +1881,8 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
        unsigned long flags;

+       VM_WARN_ON_ONCE(mem_cgroup_is_root(memcg));
+
        local_lock_irqsave(&memcg_stock.stock_lock, flags);
        __refill_stock(memcg, nr_pages);
        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);


Other than that,
Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>