Re: [PATCH v2 1/2] memcg: move mem_cgroup_swappiness and vm_swappiness to mm/swap.h

Johannes Weiner <[email protected]> Wed, 22 Jul 2026 21:59:38 -0400

Newsgroups	org.kernel.vger.cgroups,org.kernel.vger.linux-kernel,org.kvack.linux-mm
Message-ID	<[email protected]>

Acked-by: Johannes Weiner <[email protected]>

One small suggestion:

On Thu, Jul 16, 2026 at 11:17:28AM +0800, Ridong wrote:
> @@ -76,6 +77,25 @@ enum swap_cluster_flags {
>  	CLUSTER_FLAG_MAX,
>  };
>  
> +extern int vm_swappiness;
> +
> +static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
> +{
> +#ifdef CONFIG_MEMCG_V1
> +	/* Cgroup2 doesn't have per-cgroup swappiness */
> +	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
> +		return READ_ONCE(vm_swappiness);
> +
> +	/* root ? */
> +	if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
> +		return READ_ONCE(vm_swappiness);
> +
> +	return READ_ONCE(memcg->swappiness);
> +#else
> +	return READ_ONCE(vm_swappiness);
> +#endif

How about:

#ifdef CONFIG_MEMCG_V1
	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
	    !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
		return memcg->swappiness;
#endif
	return READ_ONCE(vm_swappiness);