> diff --git a/include/linux/sched/numa_balancing.h b/include/linux/sched/numa_balancing.h
> index 52b22c5c396d..792b6665f476 100644
> --- a/include/linux/sched/numa_balancing.h
> +++ b/include/linux/sched/numa_balancing.h

[ ... ]

> @@ -32,6 +33,28 @@ extern void set_numabalancing_state(bool enabled);
> extern void task_numa_free(struct task_struct *p, bool final);
> bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio,
> 				int src_nid, int dst_cpu);
> +
> +extern struct static_key_false sched_numa_balancing;
> +static inline bool task_numab_enabled(struct task_struct *p)
> +{
> +	if (static_branch_unlikely(&sched_numa_balancing))
> +		return true;
> +	return false;
> +}
> +
> +static inline bool task_numab_mode_normal(void)
> +{
> +	if (sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL)
> +		return true;
> +	return false;
> +}
> +
> +static inline bool task_numab_mode_tiering(void)
> +{
> +	if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
> +		return true;
> +	return false;
> +}
>  #else
>  static inline void task_numa_fault(int last_node, int node, int pages,
> 				   int flags)

[ ... ]

> @@ -52,6 +75,10 @@ static inline bool should_numa_migrate_memory(struct task_struct *p,
>  {
>  	return true;
>  }
> +static inline bool task_numab_enabled(struct task_struct *p)
> +{
> +	return false;
> +}
>  #endif

The #else block adds a stub for task_numab_enabled(), but task_numab_mode_normal()
and task_numab_mode_tiering() are missing from this section. These helpers are
defined when CONFIG_NUMA_BALANCING is enabled, but have no stubs when it is
disabled.

> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 670fe9fae5ba..7ee5695326e3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c

[ ... ]

> @@ -4843,9 +4844,7 @@ static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
>  	if (!current_is_kswapd() || sc->order)
>  		return false;
>
> -	mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ?
> -	       WMARK_PROMO : WMARK_HIGH;
> -
> +	mark = task_numab_mode_tiering() ? WMARK_PROMO : WMARK_HIGH;

[ ... ]

> @@ -6774,7 +6773,7 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
>  		enum zone_stat_item item;
>  		unsigned long free_pages;
>
> -		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
> +		if (task_numab_mode_tiering())
>  			mark = promo_wmark_pages(zone);

The original sysctl_numa_balancing_mode is defined to 0 when CONFIG_NUMA_BALANCING
is disabled (see include/linux/sched/sysctl.h), allowing this code to compile and
work correctly in both configurations. The new task_numab_mode_tiering() helper
lacks a stub in the #else block, so should_abort_scan() and pgdat_balanced() in
mm/vmscan.c will fail to compile when CONFIG_NUMA_BALANCING is not enabled.

Would it make sense to add stubs for task_numab_mode_normal() and
task_numab_mode_tiering() to the #else block, returning false to match the
original behavior when sysctl_numa_balancing_mode is defined as 0?


---
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