linux-kernel - Re: [PATCH 2/3] mm: use nodes_and() return value to simplify client code

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Message-ID: <88beb165-cb8a-4c13-af96-2a7e39653f17@suse.cz>
Date: Thu, 15 Jan 2026 18:22:31 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Yury Norov <ynorov@...dia.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Alistair Popple <apopple@...dia.com>,
 Byungchul Park <byungchul@...com>, David Hildenbrand <david@...nel.org>,
 Gregory Price <gourry@...rry.net>, Johannes Weiner <hannes@...xchg.org>,
 Joshua Hahn <joshua.hahnjy@...il.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Matthew Brost <matthew.brost@...el.com>, Michal Hocko <mhocko@...e.com>,
 Michal Koutný <mkoutny@...e.com>,
 Mike Rapoport <rppt@...nel.org>, Rakie Kim <rakie.kim@...com>,
 Suren Baghdasaryan <surenb@...gle.com>, Tejun Heo <tj@...nel.org>,
 Waiman Long <longman@...hat.com>, Ying Huang <ying.huang@...ux.alibaba.com>,
 Zi Yan <ziy@...dia.com>, cgroups@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
 Rasmus Villemoes <linux@...musvillemoes.dk>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm: use nodes_and() return value to simplify client
 code

On 1/14/26 18:22, Yury Norov wrote:
> establish_demotion_targets() and kernel_migrate_pages() call
> node_empty() immediately after calling nodes_and(). Now that
> nodes_and() return false if nodemask is empty, drop the latter.
> 
> Signed-off-by: Yury Norov <ynorov@...dia.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/memory-tiers.c | 3 +--
>  mm/mempolicy.c    | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 864811fff409..2cbef49a587d 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -475,8 +475,7 @@ static void establish_demotion_targets(void)
>  	 */
>  	list_for_each_entry_reverse(memtier, &memory_tiers, list) {
>  		tier_nodes = get_memtier_nodemask(memtier);
> -		nodes_and(tier_nodes, node_states[N_CPU], tier_nodes);
> -		if (!nodes_empty(tier_nodes)) {
> +		if (nodes_and(tier_nodes, node_states[N_CPU], tier_nodes)) {
>  			/*
>  			 * abstract distance below the max value of this memtier
>  			 * is considered toptier.
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 68a98ba57882..92a0bf7619a2 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1909,8 +1909,7 @@ static int kernel_migrate_pages(pid_t pid, unsigned long maxnode,
>  	}
>  
>  	task_nodes = cpuset_mems_allowed(current);
> -	nodes_and(*new, *new, task_nodes);
> -	if (nodes_empty(*new))
> +	if (!nodes_and(*new, *new, task_nodes))
>  		goto out_put;
>  
>  	err = security_task_movememory(task);